Methods and systems for enhancing control of power plant generating units

ABSTRACT

A control method for optimizing a turndown operation for a power plant having a plurality of generating units. The plurality of generating units each may include either an on-condition or an off-condition during a selected operating period. The method may include: defining competing operating modes, wherein the competing operating modes include different possible combinations regarding which of the plurality of generating units have the on-condition and which have the off-condition during the selected operating period; defining multiple cases for each of the competing operating modes, wherein the multiple cases include varying a value of an operating parameter; receiving performance objectives that include a cost function; receiving an ambient conditions forecast; for the multiple cases of the competing operating modes, simulating the turndown operation with a power plant model given the value of the operating parameter and the ambient conditions forecast; evaluating a simulation result pursuant to the cost function so to select therefrom a preferred case.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional patent applicationNo. 61/922,555 entitled “TURBINE ENGINE AND PLANT OPERATIONALFLEXIBILITY AND ECONOMIC OPTIMIZATION SYSTEMS AND PROCESSES RELATEDTHERETO” filed on Dec. 31, 2013, which provisional application isincorporated herein by reference in its entirety; this applicationclaims the benefit of the provisional's filing date under 35 U.S.C.119(e).

BACKGROUND OF THE INVENTION

The invention of the present application relates generally to powergeneration and, more particularly, to methods and systems related to theeconomic and performance optimization and/or enhancement of power plantshaving thermal generating units.

In electric power systems, a number of participants or power plantsgenerate electricity that is then distributed over common transmissionlines to residential and commercial customers. As will be appreciated,thermal generating units, such as gas turbines, steam turbines, andcombined-cycle plants, are still relied on to generate a significantportion of the power such systems require. Each of the power plantswithin such systems include one or more power generating units, and eachof these units typically includes a control system that controlsoperation, and, in case of power plants having more than one generatingunit, the performance of the power plant as a whole. As an example, oneof the responsibilities of a plant operator is the generation of anoffer curve representing the cost of power production. An offer curvetypically includes an incremental variable cost curve, an averagevariable cost curve, or another suitable indication of variable powergenerating expense, which typically is expressed in dollars permegawatt-hour versus output in megawatts. It will be appreciated that anaverage variable cost curve may represent a cumulative cost divided by acumulative power output for a given point, and an incremental variablecost curve may represent a change in cost divided by a change in poweroutput. An incremental variable cost curve may be obtained, for example,by taking a first derivative of an input-output curve of the power plantthat represents cost per hour versus power generated. In acombined-cycle power plant in which waste heat from a fuel burninggenerator is used to produce steam to power a supplemental steamturbine, an incremental variable cost curve may also be obtained withknown techniques, but its derivation may be more complex.

In most power systems, a competitive process commonly referred to aseconomic dispatch is used to divide system load among power plants overa future time period. As part of this process, power plants periodicallygenerate offer curves and send the offer curves to a power systemauthority or dispatcher. Such offer curves represent bids from the powerplants to generate a portion of the electricity required by the powersystem over a future market period. The dispatch authority receives theoffer curves from the power plants within its system and evaluates themto determine the level at which to engage each power plant so to mostefficiently satisfy the predicted load requirements of the system. Indoing this, the dispatch authority analyzes the offer curves and, withthe objective of finding the lowest generating cost for the system,produces a commitment schedule that describes the extent to which eachof the power plants will be engaged over the relevant time period.

Once the commitment schedule is communicated to the power plants, eachpower plant may determine the most efficient and cost-effective mannerby which to satisfy its load commitment. It will be appreciated that thegenerating units of the power plant include control systems that monitorand control operation. When the generating units include thermalgenerators, such control systems govern the combustion systems and otheraspects of the operation. (For illustrative purposes, both a gas turbineand combined-cycle power plants are described herein; however, it willbe appreciated that certain embodiments of the present invention may beapplied to other types of power generating units or be used inconjunction there with.) The control system may execute schedulingalgorithms that adjust the fuel flow, inlet guide vanes, and othercontrol inputs to ensure efficient operation of the engine. However, theactual output and efficiency of a power plant is impacted by externalfactors, such as variable ambient conditions, that cannot be fullyanticipated. As will be appreciated, the complexity of such systems andthe variability of operating conditions make it difficult to predict andcontrol performance, which often result in inefficient operation.

Machine degradation that occurs over time is another difficult toquantify fact, which may have a significant effect on the performance ofthe generating units. It will be appreciated that rate of degradation,replacement of worn components, timing of maintenance routines, andother factors impact the short term performance of the plant, and thusneed to be accounted for when generating cost curves during thedispatching process as well as when assessing the long termcost-effectiveness of the plant. As an example, gas turbine lifetypically includes limits expressed in both hours of operation andnumber of starts. If a gas turbine or a component thereof reaches itsstarts limit before its hours limit, it must be repaired or replaced,even if it has hours-based life remaining. Hours-based life in a gasturbine may be prolonged by reducing firing temperature, but thisreduces efficiency of the gas turbine, which increases cost ofoperation. Conversely, increasing the firing temperature increasesefficiency, but shortens gas turbine life and increases maintenanceand/or replacement costs. As will be appreciated, life cycle cost of athermal engine is dependent on many complex factors, while alsorepresenting a significant consideration in the economic efficiency ofthe power plant.

Given the complexity of modern power plants, particularly those havingmultiple generating units, and the market within which it competes,power plant operators continued to struggle to maximize economic return.For example, grid compliance and dispatch planning for a power plant isadversely impacted by controlling thermal generating units in anoverly-static manner, i.e., using static control profiles, such as heatrate curves gathered derived from only periodic performance tests.Between these periodic updates, turbine engine performance may change(e.g., from degradation), which may affect start-up and loadperformance. Moreover, intraday changes in the external factors, withoutaccounting for the same in the turbine control profiles, may lead toinefficient operation. To compensate for this type of variability, powerplant operators often become overly conservative in planning for futureoperation, which results in underutilized generating units. Other times,plant operators are forced to operate units inefficiently to satisfyover-commitments.

Without identifying the short-term inefficiencies and/or long-termdeterioration as each is realized, the conventional control systems ofpower plants either have to be retuned frequently, which is an expensiveprocess, or conservatively operated so to preemptively accommodatecomponent deterioration. The alternative is to risk violatingoperational boundaries that leads to excessive fatigue or failure.Similarly, conventional power plant control systems lack the ability tomost cost-effectively accommodate changing conditions. As will beappreciated, this results in power plant utilization that is often farfrom optimal. As such, there exists a need for improved methods andsystems for monitoring, modeling, and controlling power plant operation,particularly those that enable a more complete understanding of themyriad operating modes available to operators of complex modern powerplants and the economic trade-offs associated with each.

BRIEF DESCRIPTION OF THE INVENTION

The present application thus describes a control method for optimizing aturndown operation for a power plant having a plurality of generatingunits for a selected operating period. The plurality of generating unitseach may include either an on-condition or an off-condition during theselected operating period. The method may include the steps of: definingcompeting operating modes, wherein the competing operating modes includedifferent possible combinations regarding which of the plurality ofgenerating units have the on-condition and which have the off-conditionduring the selected operating period; defining multiple cases for eachof the competing operating modes, wherein the multiple cases includevarying a value of an operating parameter over a range; receivingperformance objectives that include a cost function for evaluating theturndown operation during the selected operating period; receiving anambient conditions forecast for the selected operating period; for eachof the multiple cases of the competing operating modes, simulating theturndown operation of the power plant for the selected operating periodwith a power plant model given the value of the operating parameters andthe ambient conditions forecast; evaluating a simulation result fromeach of the simulations pursuant to the cost function so to selecttherefrom a preferred case from the multiple cases for each of thecompeting operating modes.

These and other features of the present application will become moreapparent upon review of the following detailed description of thepreferred embodiments when taken in conjunction with the drawings andthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of a power system according to aspectsof the present invention;

FIG. 2 illustrates a schematic diagram of an exemplary thermalgenerating unit as may be employed within power plants according toembodiments of the present invention;

FIG. 3 shows a schematic diagram of an exemplary power plant having aplurality of gas turbines in accordance with embodiments of the presentinvention;

FIG. 4 illustrates an exemplary system configuration of a plantcontroller and optimizer according to aspects of the present invention;

FIG. 5 illustrates a schematic diagram of a power plant with a plantcontroller and optimizer having a system configuration according tocertain aspects of the present invention;

FIG. 6 shows a computer system having an exemplary user interfaceaccording to certain aspects of the present invention;

FIG. 7 is an exemplary incremental heat rate curve and an effect errormay have on the economic dispatch process;

FIG. 8 shows a schematic diagram of an exemplary plant controller with apower system according to aspects of the present invention;

FIG. 9 illustrates a flow diagram of power plant control methodaccording to aspects of the present invention;

FIG. 10 illustrates a data flow diagram describing an architecture for aplant optimization system for a combined cycle power plant in accordancewith aspects of the present invention;

FIG. 11 provides a simplified block diagram of a computer system as maybe employed with a real-time optimization system in accordance withaspects of the present invention;

FIG. 12 is a flow diagram of an exemplary method for solvingparameterized simultaneous equations and constraints in accordance withthe present invention;

FIG. 13 shows a simplified configuration of a computer system accordingto control methodology of embodiments of the present invention;

FIG. 14 illustrates an alternative configuration of a computer system inaccordance with control methodology of embodiments of the presentinvention;

FIG. 15 is a flow diagram of an exemplary control methodology accordingto exemplary aspects of the present invention;

FIG. 16 is a flow diagram of an alternative control methodologyaccording to exemplary aspects of the present invention;

FIG. 17 is a flow diagram of an alternative control methodologyaccording to exemplary aspects of the present invention;

FIG. 18 illustrates a flow diagram in which an alternative embodiment ofthe present invention is provided that relates to the optimization ofturndown operation;

FIG. 19 illustrates a flow diagram in which an alternative embodiment ofthe present invention is provided that relates to the optimizing betweenturndown and shutdown operation;

FIG. 20 is a diagram illustrating available operating modes of a gasturbine during a selected operating period having defined intervalsaccording to aspects of an exemplary embodiment of the presentinvention;

FIG. 21 is a diagram illustrating available operating modes of a gasturbine during a selected operating period having defined intervalsaccording to aspects of an alternative embodiment of the presentinvention;

FIG. 22 illustrates a flow diagram according to a power plant fleetoptimization process according to an alternative embodiment of thepresent invention;

FIG. 23 illustrates a schematic diagram of a power plant fleetoptimization system according to aspects of the present invention;

FIG. 24 illustrates a schematic diagram of a power plant fleetoptimization system according to alternative aspects of the presentinvention;

FIG. 25 illustrates a schematic diagram of a power plant fleetoptimization system according to alternative aspects of the presentinvention;

FIG. 26 illustrates a schematic diagram of a power block optimizationsystem that includes a block controller;

FIG. 27 illustrates a schematic diagram of an alternative power blockoptimization system that includes a block controller;

FIG. 28 is a flowchart depicting an embodiment of a process foroptimizing a shutdown of a combined cycle power plant; and

FIG. 29 illustrates an exemplary control system in which a model-freeadaptive controller is used according to aspects of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

Example embodiments of the invention will be described more fullyhereinafter with reference to the accompanying drawings, in which some,but not all embodiments are shown. Indeed, the invention may be embodiedin many different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will satisfy applicable legal requirements. Likenumbers may refer to like elements throughout.

According to aspects of the present invention, systems and methods aredisclosed which may be used to optimize the performance of powersystems, power plants, and/or thermal power generating units. Inexemplary embodiments, this optimization includes an economicoptimization by which an operator of a power plant decides betweenalternative modes of operation so to enhance profitability. Embodimentsmay be utilized within a particular power system so to provide acompetitive edge in procuring advantageous economic commitment termsduring the dispatch process. An adviser function may allow operators tomake choices between operating modes based on accurate economiccomparisons and projections. As another feature, the process ofprospectively purchasing fuel for future generating periods may beimproved so that fuel inventory is minimized, while not increasing therisk of a shortfall. Other configurations of the present invention, asdescribed below, provide computer-implemented methods and apparatus formodeling power systems, and power plants having multiple thermalgenerating units. Technical effects of some configurations of thepresent invention include the generation and solution of energy systemmodels that predict performance under varying physical, operational,and/or economic conditions. Exemplary embodiments of the presentinvention combine a power plant model that predicts performance undervarying ambient and operational conditions with an economic model thatincludes economic constraints, objectives, and market conditions so tooptimize profitability. In doing this, the optimization system of thepresent invention may predict optimized setpoints that maximizeprofitability for particular combinations of ambient, operational,contractual, regulatory, legal, and/or economic and market conditions.

FIG. 1 illustrates a schematic representation of a power system 10 thatincludes aspects of the present invention as well as an exemplaryenvironment in which embodiments may operate. Power system 10 mayinclude power generators or plants 12, such as, for example, theillustrated wind and thermal power plants. It will be appreciated thatthermal power plants may include generating units such as gas turbines,coal-fired steam turbines, and/or combined-cycle plants. In addition,power system 10 may include other types of power plants (not shown),such as solar power installations, hydroelectric, geothermal, nuclear,and/or any other suitable power sources now known or discoveredhereafter. Transmission lines 14 may connect the various power plants 12to customers or loads 16 of power system 10. It should be understoodthat transmission lines 14 represent a grid or distribution network forthe power system and may include multiple sections and/or substations asmay be desired or appropriate. The power generated from power plants 12may be delivered via transmission lines 14 to loads 16, which, forexample, may include municipalities, residential, or commercialcustomers. Power system 10 may also include storage devices 18 that areconnected to transmission lines 14 so to store energy during periods ofexcess generation.

Power system 10 also includes control systems or controllers 22, 23, 25that manage or control the operation of several of the componentscontained therein. For example, a plant controller 22 may control theoperation of each of the power plants 12. Load controllers 23 maycontrol the operation of the different loads 16 that are part of thepower system 10. For example, a load controller 23 may manage the manneror timing of a customer's power purchase. A dispatch authority 24 maymanage certain aspects of the operation of power system 10, and mayinclude a power system controller 25 that controls the economic dispatchprocedure by which load commitments are distributed among participatingpower plants. Controllers 22, 23, 25, which are represented byrectangular blocks, may be connected via communications lines orconnections 21 to a communications network 20 over which data isexchanged. The connections 21 may be wired or wireless. It will beappreciated that communications network 20 may be connected to or partof a larger communications system or network, such as the internet or aprivate computer network. In addition, the controllers 22, 23, 25 mayreceive information, data, and instructions from and/or sendinformation, data, and instructions to data libraries and resources,which may be referred to herein generally as “data resources 26”,through communications network 20, or, alternatively, may store or houseone or more such data repositories locally. Data resources 26 mayinclude several types of data, including but not limited to: marketdata, operating data, and ambient data. Market data includes informationon market conditions, such as energy sales price, fuel costs, laborcosts, regulations, etc. Operating data includes information relating tothe operating conditions of the power plant or its generating units,such as temperature or pressure measurements within the power plant, airflow rates, fuel flow rates, etc. Ambient data includes informationrelated to ambient conditions at the plant, such as ambient airtemperature, humidity, and/or pressure. Market, operating, and ambientdata each may include historical records, present condition data, and/ordata relating to forecasts. For example, data resources 26 may includepresent and forecast meteorological/climate information, present andforecast market conditions, usage and performance history records aboutthe operation of the power plant, and/or measured parameters regardingthe operation of other power plants having similar components and/orconfigurations, as well as other data as may be appropriate and/ordesired. In operation, for example, power system controller 25 ofdispatch authority 24 may receive data from and issue instructions tothe other controllers 22, 23 within power system 10. Each of the plantand the load controllers then controls the system component for which itis responsible and relays information about it to and receiveinstruction from power system controller 25.

FIG. 2 is a schematic diagram of an exemplary thermal generating unit, agas turbine system 30, that may be used within a power plant accordingto the present invention. As illustrated, gas turbine system 30 includesa compressor 32, a combustor 34, and a turbine 36 that is drivinglycoupled to the compressor 32, as well as a component controller 31. Thecomponent controller 31 may connect to the plant controller 22, whichmay connect to an user input device for receiving communications from anoperator 39. Alternatively, it will be appreciated that the componentcontroller 31 and the plant controller 22 may be combined into a singlecontroller. An inlet duct 40 channels ambient air to the compressor 32.As discussed in FIG. 3, injected water and/or other humidifying agentmay be channeled to the compressor through inlet duct 40. Inlet duct 40may have filters, screens and sound absorbing devices that contribute toa pressure loss of ambient air flowing through inlet duct 40 into inletguide vanes 41 of compressor 32. An exhaust duct 42 channels combustiongases from an outlet of turbine 36 through, for example, emissioncontrol and sound absorbing devices. The sound adsorbing materials andemission control devices may apply a backpressure to the turbine 36. Theturbine 36 may drive a generator 44 that produces electrical power,which then may be distributed through power system 10 via transmissionlines 14.

The operation of the gas turbine system 30 may be monitored by severalsensors 46 that detect various operating conditions or parametersthroughout it, including, for example, conditions within the compressor32, combustor 34, turbine 36, generator 44, and ambient environment 33.For example, temperature sensors 46 may monitor ambient temperatures,compressor discharge temperature, turbine exhaust temperature, and othertemperatures within the flow path of the gas turbine system 30.Likewise, the pressure sensors 46 may monitor ambient pressure, staticand dynamic pressure levels at the compressor inlet, compressor outlet,turbine exhaust, and that other suitable locations within the gasturbine system. Humidity sensors 46, such as wet and thy bulbthermometers, may measure ambient humidity in the inlet duct of thecompressor. Sensors 46 may also include flow sensors, speed sensors,flame detector sensors, valve position sensors, guide vane angle sensorsand other sensors that are typically used to measure various operatingparameters and conditions relative to the operation of the gas turbinesystem 30. As used herein, the term “parameter” refers to measurablephysical properties of operation which may be used to define theoperating conditions within a system, such as gas turbine system 30 orother generating system described herein. Operating parameters mayinclude temperature, pressure, humidity and gas flow characteristics atlocations defined along the path of the working fluid, as well asambient conditions, fuel characteristics, and other measurables as maybe suitable without limit. It will be appreciated that control system 31also includes several actuators 47 by which it mechanically controls theoperation of the gas turbine system 30. Actuators 47 may includeelectro-mechanical devices having variable setpoints or settings thatallow the manipulation of certain process inputs (i.e., manipulatedvariables) for the control of process outputs (i.e., controlledvariables) in accordance with a desired result or mode of operation. Forexample, commands generated by the component controller 31 may cause oneor more actuators 47 within the turbine system 30 to adjust valvesbetween the fuel supply and combustor 34 that regulate the flow level,fuel splits, and/or type of fuel being combustor. As another example,commands generated by control system 31 may cause one or more actuatorsto adjust an inlet guide vane setting that alters their angle oforientation.

The component controller 31 may be a computer system having a processorthat executes program code to control the operation of the gas turbinesystem 30 using sensor measurements and instructions from user or plantoperator (hereinafter “operator 39”). As discussed in more detail below,software executed by the controller 31 may include scheduling algorithmsfor regulating any of the subsystems described herein. The componentcontroller 31 may regulate gas turbine system 30 based, in part, onalgorithms stored in its digital memory. These algorithms, for example,may enable the component controller 31 to maintain the NOx and COemissions in the turbine exhaust to within certain predefined emissionlimits, or, in another instance, maintain the combustor firingtemperature to within predefined limits. It will be appreciated thatalgorithms may include inputs for parameter variables such as compressorpressure ratio, ambient humidity, inlet pressure loss, turbine exhaustbackpressure, as well as any other suitable parameters. The schedulesand algorithms executed by the component controller 31 accommodatevariations in ambient conditions that affect emissions, combustordynamics, firing temperature limits at full and part-load operatingconditions, etc. As discussed in more detail below, the componentcontroller 31 may apply algorithms for scheduling the gas turbine, suchas those setting desired turbine exhaust temperatures and combustor fuelsplits, with the objective of satisfying performance objectives whilecomplying with operability boundaries of the gas turbine system. Forexample, the component controller 31 may determine combustor temperaturerise and NOx during part-load operation in order to increase theoperating margin to the combustion dynamics boundary and thereby improveoperability, reliability, and availability of the generating unit.

Turning to FIG. 3, a schematic diagram is provided of an exemplary powerplant 12 having a plurality of generating units or plant components 49in accordance with aspects of the present invention. The illustratedpower plant 12 of FIG. 3 is a common configuration, and thus will beused to discuss several of the exemplary embodiments of the presentinvention that are presented below. However, as will be appreciated, themethods and systems described herein may be more generally applicableand scalable to power plants having more generating units than thoseshown in FIG. 3, while still also applicable to power plants having asingle generating component such as the one illustrated in FIG. 2. Itwill be appreciated that the power plant 12 of FIG. 3 is acombined-cycle plant that includes several plant components 49,including a gas turbine system 30 and a steam turbine system 50. Powergeneration may be augmented by other plant components 49, such as aninlet conditioning system 51 and/or a heat recovery steam generatorhaving a duct firing system (hereinafter, “HRSG duct firing system 52”).It will be appreciated that each of the gas turbine system 30, the steamturbine system 50 that includes the HRSG duct firing system 52, and theinlet conditioning system 51 includes a control system or the componentcontroller 31 that communicates electronically with sensors 46 andactuators 47 that are dedicated to each plant component. As used herein,the inlet conditioning system 51, unless otherwise stated, may refer tocomponents used to condition air before entering the compressor, whichmay include an inlet chilling system or chiller, evaporator, fogger,water injection system, and/or, in some alternative cases, a heatingelement.

In operation, the inlet conditioning system 51 cools the air enteringthe gas turbine system 30 so to enhance the power generating capacity ofthe unit. The HRSG duct firing system 52 burns fuel to provideadditional heat so to increase the supply of steam that is expandedthrough a turbine 53. In this manner the HRSG duct firing system 52augments the energy supplied by the hot exhaust gases 55 from the gasturbine system, and thereby increases the power generating capacity ofthe steam turbine system.

By way of exemplary operation, the power plant 12 of FIG. 3 directs aflow of fuel to the combustor 34 of gas turbine system 30 forcombustion. The turbine 36 is powered by combustion gases and drives thecompressor 32 and generator 44, which delivers electrical energy to thetransmission lines 14 of the power system 10. The component controller31 of gas turbine system 30 may set commands for the gas turbine systemregarding fuel flow rate and receive sensor data from the gas turbinesystem, such as the air inlet temperature, humidity, power output, shaftspeed, and temperatures of the exhaust gas. The component controller 31may also collect other operating data from pressure and temperaturesensors, flow control devices and other devices monitoring the operationof the gas turbine system. The component controller 31 may send dataregarding the operation of the gas turbine system and receiveinstruction from the plant controller 22 regarding setpoints foractuators that control process inputs.

During certain modes of operation, the air entering gas turbine system30 may be cooled or otherwise conditioned by inlet conditioning system51 so to augment the generating capacity of gas turbine system. Theinlet conditioning system 51 may include a refrigeration system 65 forcooling water, and a component controller 31 that controls itsoperation. In this instance, the component controller 31 may receiveinformation regarding the temperature of the cooling water as well asinstruction regarding the desired level of injection, which may comefrom the plant controller 22. The component controller 31 of inletconditioning system 51 may also issue commands causing refrigerationsystem 65 to produce cooling water having a certain temperature and flowrate. The component controller 31 of inlet conditioning system 51 maysend data regarding the operation of the inlet conditioning system 51.

Steam turbine system 50 may include turbine 53 and HRSG duct firingsystem 52, as well as a component controller 31 that, as illustrated, isdedicated to the control of its operation. Hot exhaust gases 55 fromexhaust ducts of the gas turbine system 30 may be directed into thesteam turbine system 50 to produce the steam that is expanded throughthe turbine 53. As will be appreciated, HRSG duct firing systems areregularly used to provide additional energy for the production of steamso to increase the generating capacity of a steam turbine system. Itwill be appreciated that the rotation induced within the turbine 53 bythe steam drives a generator 44 so to produce electrical energy that maybe then sold within power system 10 across transmission lines 14. Thecomponent controller 31 of the steam turbine system 50 may set the flowrate of fuel burned by the duct firing device 52 and thereby increasethe generation of steam beyond the amount that may be produced withexhaust gases 55 alone. The component controller 31 of the steam turbinesystem 50 may send data regarding the operation of that the plantcomponent 49 and receive therefrom instruction as to how it shouldoperate.

The plant controller 22 of FIG. 3, as illustrated, may be connected toeach of the component controllers 31 and, via these connections,communicate with sensors 46 and actuators 47 of the several plantcomponents 49. As part of controlling the power plant 12, the plantcontroller 22 may simulate its operation. More specifically, the plantcontroller 22 may include or communicate with digital models (or simply“models”) that simulate the operation of each plant component 49. Themodel may include algorithms that correlate process input variables toprocess output variables. The algorithms may include sets ofinstructions, logic, mathematical formula, functional relationshipdescriptions, schedules, data collections, and/or the like. In thisinstance, the plant controller 22 includes: a gas turbine model 60,which models the operation of the gas turbine system 30; an inletconditioning system model 61, which models the operation of inletconditioning system 51; and a steam turbine model 62, which models theoperation of the steam turbine system 50 and the HRSG duct firing system52. As a general note, it will be appreciated that the systems and theirrelated models, as well as the discrete steps of the methods providedherein, may be subdivided and/or combined in various ways withoutmaterially deviating from the scope of the present invention, and thatthe manner in which each are described is exemplary unless otherwisestated or claimed. Using these models, the plant controller 22 maysimulate the operation, e.g., thermodynamic performance or parametersdescribing operation, of the power plant 12.

The plant controller 22 may then use results from the simulations so todetermine optimized operating modes. Such optimized operating modes maybe described by parameter sets that include a plurality of operatingparameters and/or setpoints for actuators and/or other operatingconditions. As used herein, the optimized operating mode is one that, atminimum, is preferable over at least one alternative operating modepursuant to defined criteria or performance indicators, which may beselected by an operator to evaluate plant operation. More specifically,optimized operating modes, as used herein, are those that are evaluatedas preferable over one or more other possible operating modes which werealso simulated by the plant model. The optimized operating modes aredetermined by evaluating how the model predicts the power plant willoperate under each. As discussed below, an optimizer 64, e.g., a digitalsoftware optimization program, may run the digital power plant modelpursuant to various parameter sets and, then, identify preferable oroptimized modes of operation by evaluating the results. The variationsin the setpoints may be generated by perturbations applied around thesetpoints chosen for analysis. These may be based in part on historicaloperation. It will be appreciated that the optimized operating mode maybe determined by the optimizer 64 based on one or more defined costfunctions. Such cost functions, for example, may regard a cost toproduce power, profitability, efficiency, or some other criteria asdefined by the operator 39.

To determine costs and profitability, the plant controller 22 mayinclude or be in communication with an economic model 63 that tracks theprice of power and certain other variable costs, such as the costs ofthe fuel used in the gas turbine system, the inlet conditioning system,and HRSG duct firing system. The economic model 63 may provide the dataused by the plant controller 22 to judge which of the proposed setpoints(i.e., those chosen setpoints for which operation is modeled fordetermining optimized setpoints) represents minimal production costs ormaximum profitability. According to other embodiments, as discussed inmore detail with FIG. 4, the optimizer 64 of the plant controller 22 mayinclude or operate in conjunction with a filter, such as a Kalmanfilter, to assist in tuning, adjusting and calibrating the digitalmodels so that the models accurately simulate the operation of the powerplant 12. As discussed below, the model may be a dynamic one thatincludes a learning mode in which it is tuned or reconciled viacomparisons made between actual operation (i.e., values for measuredoperating parameters that reflect the actual operation of the powerplant 12) and predicted operation (i.e., values for the same operatingparameters that the model predicted). As part of the control system, thefilter also may be used to adjust or calibrate the models in real timeor in near real time, such as every few minutes or hour or as specified.

The optimized setpoints generated by the plant controller 22 representsa recommended mode of operation and, for example, may include fuel andair settings for the gas turbine system, the temperature and water massflow for the inlet conditioning system, the level of duct firing withinthe steam turbine system 50. According to certain embodiments, thesesuggested operating setpoints may be provided to the operator 39 via aninterface device such as a computer display screen, printer, or soundspeaker. Knowing the optimized setpoints, the operator then may inputthe setpoints into the plant controller 22 and/or the componentcontroller 31, which then generates control information for achievingthe recommended mode of operation. In such embodiments where theoptimized setpoints do not include specified control information forachieving the operating mode, the component controllers may provide thenecessary control information for this and, as discussed in more detailbelow, may continue controlling the plant component in a closed loopmanner pursuant to the recommended operating mode until the nextoptimization cycle. Depending on operator preference, the plantcontroller 22 also may directly or automatically implement optimizedsetpoints without operator involvement.

By way of exemplary operation, the power plant 12 of FIG. 3 directs aflow of fuel to combustor 34 of the gas turbine system 30 forcombustion. The turbine 36 is powered by combustion gases to drive thecompressor 32 and the generator 44, which delivers electrical energy totransmission lines 14 of the power system 10. The component controller31 may set commands for the gas turbine system 30 regarding fuel flowrate and receive sensor data from the gas turbine system 30 such as theair inlet temperature and humidity, power output, shaft speed andtemperatures of the exhaust gas. The component controller 31 may alsocollect other operating data from pressure and temperature sensors, flowcontrol devices and other devices monitoring the gas turbine system 30.The component controller 31 of the gas turbine system 30 may send dataregarding the operation of the system and receive instruction from theplant controller 22 regarding setpoints for actuators that controlprocess inputs.

During certain modes of operation, the air entering gas turbine system30 may be cooled by cold water supplied to the inlet air duct 42 fromthe inlet conditioning system 51. It will be appreciated that coolingthe air entering a gas turbine may be done to augment the capacity ofthe gas turbine engine to generate power. The inlet conditioning system51 includes a refrigeration system or refrigerator 65 for cooling water,and a component controller 31. In this instance, the componentcontroller 31 receives information regarding the temperature of thecooling water and commands regarding the desired cooling of the intakeair. These commands may come from the plant controller 22. The componentcontroller 31 of inlet conditioning system 51 may also issue commands tocause refrigeration system 65 to produce cooling water having a certaintemperature and flow rate. The component controller 31 of inletconditioning system 51 may send data regarding the operation of theinlet conditioning system 51 and receive instruction from the controller22.

The steam turbine system 50, which may include a HRSG with a duct firingdevice 52, a steam turbine 53, and a component controller 31 that may bededicated to its operation. Hot exhaust gases 55 from an exhaust duct 42of the gas turbine system 30 is directed into the steam turbine system50 to produce the steam that drives it. The HRSG duct firing system 52may be used to provide additional heat energy to produce steam so toincrease the generating capacity of steam turbine system 50. The steamturbine 53 drives generator 44 to produce electrical energy that isdelivered to the power system 10 via the transmission lines 14. Thecomponent controller 31 of the steam turbine system 50 may set the flowrate of fuel burned by the duct firing device 52. Heat generated by theduct firing device increases the generation of steam beyond the amountproduced by exhaust gases 55 from turbine 36 alone. The componentcontroller 31 of the steam turbine system 50 may send data regarding theoperation of the system to and receive instruction from the plantcontroller 22.

The plant controller 22 may communicate with the operator 39 and dataresources 26, for example, to receive data on market conditions such asprices and demand for power delivered. According to certain embodiments,the plant controller 22 issues recommendations to the operator 39regarding desired operating setpoints for the gas turbine system 30,inlet conditioning system 51, and steam turbine system 50. The plantcontroller 22 may receive and store data on the operation of thecomponents and subsystems of the power plant 12. The plant controller 22may be a computer system having a processor and memory storing data, thedigital models 60, 61, 62, 63, the optimizer 64 and other computerprograms. The computer system may be embodied in a single physical orvirtual computing device or distributed over local or remote computingdevices. The digital models 60, 61, 62, 63 may be embodied as a set ofalgorithms, e.g. transfer functions, that relate operating parameters ofeach of the systems. The models may include a physics-basedaero-thermodynamic computer model, a regression-fit model, or othersuitable computer-implemented model. According to preferred embodiments,the models 60, 61, 62, 63 may be regularly, automatically and inreal-time or near real-time tuned, adjusted or calibrated or tunedpursuant to ongoing comparisons between predicted operation and themeasured parameters of actual operation. The models 60, 61, 62, 63 mayinclude filters that receives data inputs regarding actual physical andthermodynamic operating conditions of the combined-cycle power plant.These data inputs may be supplied to the filter in real-time orperiodically every 5 minutes, 15 minutes, hour, day, etc. during theoperation of the power plant 12. The data inputs may be compared to datapredicted by the digital models 60, 61, 62, 63 and, based on thecomparisons, the models may be continuously refined.

FIG. 4 illustrates a schematic system configuration of a plantcontroller 22, which includes a filter 70, an artificial neural networkconfiguration 71 (“neural network 71”), and an optimizer 64, accordingto aspects of the present invention. The filter 70, which, for example,may be a Kalman filter, may compare the actual data 72 of measuredoperating parameters from sensors 46 of the power plant 12 to predicteddata 73 of the same operating parameters by the models 60, 61, 62, 63and neural network 71, which is simulating the operation of the powerplant 12. Differences between the actual data and predicted data thenmay be used by the filter 70 to tune the model of the power plantsimulated by the neural network 71 and digital models.

It should be understood that while certain aspects of the presentinvention are described herein with reference to models in the form ofneural network based models, it is contemplated that the presentinvention may be implemented using other types of models, including butnot limited to, physics-based models, data-driven models, empiricallydeveloped models, models based upon heuristics, support vector machinemodels, models developed by linear regression, models developed using“first principles” knowledge, etc. Additionally, to properly capture therelationship between the manipulated/disturbance variables and thecontrolled variables, according to certain preferred embodiments, thepower plant model may have one or more of the followingcharacteristics: 1) nonlinearity (a nonlinear model is capable ofrepresenting a curve rather than a straight line relationship betweenmanipulated/disturbance and controlled variables); 2) multipleinput/multiple output (the model may be capable of capturing therelationships between multiple inputs—the manipulated and disturbancevariables—and multiple outputs—controlled variables); 3) dynamic(changes in the inputs may not instantaneously affect the outputs,rather there may be a time delay that is followed by a dynamic responseto the changes, for example, it may take several minutes for changes inthe inputs to fully propagate through the system. Since optimizationsystems execute at a predetermined frequency, the model must representthe effects of these changes over time and take them into account); 4)adaptive (the model may be updated at the beginning of each optimizationto reflect the current operating conditions); and 5) derived fromempirical data (since each power plant is unique, the model may bederived from empirical data obtained from the power generating unit).Given the foregoing requirements, a neural network based approach is apreferred technology for implementing the necessary plant models. Neuralnetworks may be developed based upon empirical data using advancedregression algorithms. As will be appreciated, neural networks arecapable of capturing the nonlinearity commonly exhibited in theoperation of the power plant components. Neural networks can also beused to represent systems with multiple inputs and outputs. In addition,neural networks can be updated using either feedback biasing or on-lineadaptive learning. Dynamic models can also be implemented in a neuralnetwork based structure. A variety of different types of modelarchitectures have been used for implementation of dynamic neuralnetworks. Many of the neural network model architectures require a largeamount of data to successfully train the dynamic neural network. Given arobust power plant model, it is possible to compute the effects ofchanges in the manipulated variables on the controlled variables.Furthermore, since the plant model is dynamic, it is possible to computethe effects of changes in the manipulated variables over a future timehorizon.

The filter 70 may generate performance multipliers applied to inputs oroutputs of the digital models and neural network or modify the weightsapplied to the logic units and algorithms used by the digital models andneural network. These actions by the filter reduce the differencesbetween the actual condition data and the predicted data. The filtercontinues to operate to reduce the differences further or addressfluctuations that may occur. By way of example, the filter 70 maygenerate performance multipliers for the predicted data regarding thecompressor discharge pressure and temperature in the gas turbine, theefficiency of the gas and steam turbines, the flow of fuel to the gasturbine system, the inlet conditioning system, and HRSG duct firingsystem, and/or other suitable parameters. It will be appreciated thatthese categories of operating data reflect operating parameters that aresubject to degradation of performance over time. By providingperformance multipliers for these types of data, the filter 70 may beparticularly useful in adjusting the models and neural network toaccount for degradation in the performance of the power plant.

As illustrated in FIG. 4, according to certain embodiments of thepresent invention, each of the digital models 60, 61, 62, 63 of theseveral plant components 49 of the power plant of FIG. 3 includesalgorithms, which are represented by the several graphs, that are usedto model the corresponding systems. The models interact and communicatewithin the neural network 71, and it will be appreciated that, in doingso, the neural network 71 forms a model of the entire combined-cyclepower plant 12. In this manner, the neural network simulatesthermodynamic and economic operation of the plant. As indicated by thesolid arrows in FIG. 4, the neural network 71 collects data outputted bymodels 60, 61, 62, 63 and provides data to be used as inputs by thedigital models.

The plant controller 22 of FIG. 4 also includes an optimizer 64, such asan computer program, that interacts with the neural network 71 to searchfor optimal setpoints for the gas turbine system, inlet conditioningsystem, steam turbine system, and HRSG duct firing system to achieve adefined performance objective. The performance objective, for example,may be to maximize the profitability of the power plant. The optimizer64 may cause the neural network 71 to run the digital models 60, 61, 62,63 at various operational setpoints. The optimizer 64 may haveperturbation algorithms that assist in varying the operational setpointsof the models. The perturbation algorithms cause the simulation of thecombine cycle power plant provided by the digital models and neuralnetwork to operate at setpoints different than the current operationalsetpoint for the plant. By simulating the operation of the power plantat different setpoints, the optimizer 64 searches for operationalsetpoints that would cause the plant to operate more economically orimprove performance by some other criteria, which may be defined byoperator 39.

According to exemplary embodiments, economic model 63 provides data usedby the optimizer 64 to determine which setpoints are most profitable.Economic model 63, for example, may receive and store fuel cost dataformatted such as a chart 630 that correlates the cost of fuel overtime, such as during the seasons of a year. Another chart 631 maycorrelate the price received for electrical power at different times ofa day, week or month. Economic model 63 may provide data regarding theprice received for power and the cost of fuel (gas turbine fuel, ductfiring fuel and inlet conditioning system fuel) used to produce it. Thedata from economic model 63 may be used by the optimizer 64 to evaluateeach of the operational states of the power plant pursuant to operatordefined performance objectives. The optimizer 64 may identify which ofthe operational states of the power plant 12 is optimal (which, as usedherein, means at least preferable over an alternative operational state)given the performance objectives as defined by operator 39. Asdescribed, the digital models may be used to simulate the operation ofthe plant components 49 of the power plant 12, such as modelingthermodynamic operation of the gas turbine system, the inletconditioning system, or the steam turbine system. The models may includealgorithms, such as mathematical equations and look-up tables, which maybe stored locally and updated periodically or acquired remotely via dataresources 26, that simulate the response of plant components 49 tospecific input conditions. Such look-up tables may include measuredoperating parameters describing the operation of the same type ofcomponents that operate at remote power plant installations.

Thermal model 60 of gas turbine system 30, for example, includes analgorithm 600 that correlates the effect of the temperature of inlet airto power output. It will be appreciated that this algorithm may showthat power output decreases from a maximum value 601 as the inlet airtemperature increases beyond a threshold 602 temperature. Model 60 mayalso include an algorithm 603 that correlates the heat rate of the gasturbine at different power output levels of the engine. As discussed,heat rate represents the efficiency of a gas turbine engine or otherpower generating unit, and is inversely related to efficiency. A lowerheat rate indicates a higher thermodynamic performance efficiency.Digital model 61 may simulate thermodynamic operation of the inletconditioning system 51. In this case, for example, digital model 61includes an algorithm 610 that correlates the chilling capacity based onenergy applied to run refrigeration system 65 of inlet conditioningsystem 51, so that the calculated chilling capacity indicates the amountof cooling applied to the air entering the gas turbine. There may be amaximum chilling capacity value 611 that can be achieved byrefrigeration system 65. In another case, a related algorithm 612 maycorrelate the energy applied to run refrigeration system 65 to thetemperature of the chilled air entering compressor 32 of gas turbinesystem 30. Model 61 may show, for example, that the power required torun the inlet conditioning system increases dramatically when reducingthe temperature of the air entering the gas turbine below the dew point613 of ambient air. In the case of steam turbine system 50, digitalmodel 62 may include an algorithm 620 that correlates the power outputof the steam turbine system to the energy added by HRSG duct firingsystem 52, such as the amount of fuel consumed by duct firing. Model 62may indicate, for example, that there is an upper threshold level 621 tothe increase in steam turbine system output that can be achieved by theHRSG duct firing system, which may be included in algorithm 620.

According to certain embodiments of the present invention, asillustrated in FIG. 4, the neural network 71 may interact with andprovide communications between each of the digital models of the severalplant components 49 of the power plant 12 of FIG. 3. The interaction mayinclude collecting output data from the models and generating input dataused by the models to generate further output data. The neural network71 may be a digital network of connected logic elements. The logicelements may each embody an algorithm that accepts data inputs togenerate one or more data outputs. A simple logic element may sum thevalues of the inputs to produce output data. Other logic elements maymultiply values of the inputs or apply other mathematical relationshipsto the input data. The data inputs to each of the logic elements of theneural network 71 may be assigned a weight, such as multiplier betweenone and zero. The weights may be modified during a learning mode whichadjusts the neural network to better model the performance of the powerplant. The weights may also be adjusted based on commands provided bythe filter. Adjusting the weights of the data inputs to the logic unitsin the neural network is one example of the way in which the neuralnetwork may be dynamically modified during operation of thecombined-cycle power plant. Other examples include modifying weights ofdata inputs to algorithms (which are an example of a logic unit) in eachof thermodynamic digital models for the steam turbine system, inletconditioning system, and gas turbine. The plant controller 22 may bemodified in other ways, such as, adjustments made to the logic units andalgorithms, based on the data provided by the optimizer and/or filter.

The plant controller 22 may generate an output of recommended oroptimized setpoints 74 for the combined-cycle power plant 12, which, asillustrated, may pass through an operator 39 for approval before beingcommunicated and implemented by power plant actuators 47. Asillustrated, the optimized setpoints 74 may include input from or beapproved by the operator 39 via a computer system such as the onedescribed below in relation to FIG. 6. The optimized setpoints 74 mayinclude, for example, a temperature and mass flow rate for the coolingwater generated by the inlet conditioning system and used to cool theair entering the gas turbine system; a fuel flow rate to the gas turbinesystem; and a duct firing rate. It will be appreciated that optimizedsetpoints 74 also may be then used by the neural network 71 and models60, 61, 62, 63 so that the ongoing plant simulation may predictoperating data that may later be compared to actual operating data sothat the plant model may continually be refined.

FIG. 5 illustrates a simplified system configuration of a plantcontroller 22 with an optimizer 64 and power plant model 75. In thisexemplary embodiment, the plant controller 22 is shown as a systemhaving the optimizer 64 and power plant model 75 (which, for example,includes the neural network 71 and models 60, 61, 62, 63 discussed abovein relation to FIG. 4). The power plant model 75 may simulate theoverall operation of a power plant 12. In accordance with theillustrated embodiment, the power plant 12 includes a plurality ofgenerating units or plant components 49. The plant component 49, forexample, may include thermal generating units, or other plant subsystemsas already described, each of which may include corresponding componentcontrollers 31. The plant controller 22 may communicate with thecomponent controllers 31, and through and by the component controllers31, may control the operation of the power plant 12 via connections tosensors 46 and actuators 47.

It will be appreciated that power plants have numerous variablesaffecting their operation. Each of these variables may be generallycategorized as being either input variables or output variables. Inputvariables represent process inputs, and include variables that can bemanipulated by plant operators, such as air and fuel flow rates. Inputvariables also include those variables that cannot be manipulated, suchas ambient conditions. Output variables are variables, such as poweroutput, that are controlled by manipulating those input variables thatmay be manipulated. A power plant model is configured to represent thealgorithmic relationship between input variables, which include thosethat can be manipulated, or “manipulated variables”, and those thatcannot be manipulated, or “disturbance variables”, and output orcontrolled variables, which will be referred to as “controlledvariables”. More specifically, manipulated variables are those that maybe varied by the plant controller 22 to affect controlled variables.Manipulated variables include such things as valve setpoints thatcontrol fuel and air flow. Disturbance variables refer to variables thataffect controlled variables, but cannot be manipulated or controlled.Disturbance variables include ambient conditions, fuel characteristics,etc. The optimizer 64 determines an optimal set of setpoint values forthe manipulated variables given: (1) performance objectives of the powerplant (e.g., satisfying load requirements while maximizingprofitability); and (2) constraints associated with operating the powerplant (e.g., emissions and equipment limitations).

According to the present invention, an “optimization cycle” may commenceat a predetermined frequency (e.g., every 5 to 60 seconds, or 1 to 30minutes). At the commencement of an optimization cycle, the plantcontroller 22 may obtain present data for manipulated variables,controlled variables and disturbance variables from the componentcontrollers 31 and/or directly from sensors 46 of each of the plantcomponents 49. The plant controller 22 then may use power plant model 75to determine optimal setpoint values for the manipulated variables basedupon the present data. In doing this, the plant controller 22 may runthe plant model 75 at various operational setpoints so to determinewhich set of operational setpoints are most preferable given theperformance objectives for the power plant, which may be referred to as“simulation runs”. For example, a performance objective may be tomaximize the profitability. By simulating the operation of the powerplant at different setpoints, the optimizer 64 searches for the set ofsetpoints which the plant model 75 predicts causes the plant to operatein an optimal (or, at least, preferable manner). As stated, this optimalset of setpoints may be referred to as “optimized setpoints” or an“optimized operating mode”. Typically, in arriving at the optimizedsetpoints, the optimizer 64 will have compared numerous sets ofsetpoints and the optimized setpoints will be found superior to each ofthe other sets given the performance objections defined by the operator.The operator 39 of the power plant 12 may have the option of approvingthe optimized setpoints or the optimized setpoints may be approvedautomatically. The plant controller 22 may send the optimized setpointsto the component controller 31 or, alternatively, directly to theactuators 47 of the plant components 49 so that settings may be adjustedpursuant to the optimized setpoints. The plant controller 22 may be runin a closed loop so to adjust setpoint values of the manipulatedvariables at a predetermined frequency (e.g., every 0-30 seconds or morefrequently) based upon the measured current operating conditions.

The optimizer 64 may be used to minimize a “cost function” subject to aset of constraints. The cost function essentially is a mathematicalrepresentation of a plant performance objective, and the constraints areboundaries within which the power plant must operate. Such boundariesmay represent legal, regulatory, environmental, equipment, or physicalconstraints. For instance, to minimize NOx, the cost function includes aterm that decreases as the level of NOx decreases. One common method forminimizing such a cost function, far example, is known as “gradientdescent optimization.” Gradient descent is an optimization algorithmthat approaches a local minimum of a function by taking stepsproportional to the negative of the gradient (or the approximategradient) of the function at the current point. It should be understoodthat a number of different optimization techniques may be used dependingon the form of the model and the costs and constraints. For example, itis contemplated that the present invention may be implemented by using,individually or in combination, a variety of different types ofoptimization approaches. These optimization approaches include, but notlimited to, linear programming, quadratic programming, mixed integernon-linear programming, stochastic programming, global non-linearprogramming, genetic algorithms, and particle/swarm techniques.Additionally, plant model 75 may be dynamic so that effects of changesare taken into account over a future time horizon. Therefore, the costfunction includes terms over a future horizon. Because the model is usedto predict over a time horizon, this approach is referred to as modelpredictive control, which is described in S. Piche, B. Sayyar-Rodsari,D. Johnson and M. Gerules, “Nonlinear model predictive control usingneural networks,” IEEE Control Systems Magazine, vol. 20, no. 2, pp.53-62, 2000, and which is fully incorporated herein by reference.

Constraints may be placed upon both process inputs (which includesmanipulated variables) and process outputs (which includes controlledvariables) of the power plant over the future time horizon. Typically,constraints that are consistent with limits associated with the plantcontroller are placed upon the manipulated variables. Constraints on theoutputs may be determined by the problem that is being solved. Accordingto embodiments of the present invention and as a step in theoptimization cycle, the optimizer 64 may compute the full trajectory ofmanipulated variable moves over the future time horizon, for example onehour. Thus, for an optimization system that executes every 30 seconds,120 values may be computed over an one hour future time horizon for eachmanipulated variable. Since plant model or performance objectives orconstraints may change before the next optimization cycle, the plantcontroller 22/optimizer 64 may only outputs the first value in the timehorizon for each manipulated variable to component controllers 31 asoptimized setpoints for each respective manipulated variable. At thenext optimization cycle, the plant model 75 may be updated based uponthe current conditions. The cost function and constraints also may beupdated if they have changed. The optimizer 64 then maybe used torecompute the set of values for the manipulated variables over the timehorizon and the first value in the time horizon, for each manipulatedvariable, is output to the component controller 31 as setpoint valuesfor each respective manipulated variable. The optimizer 64 may repeatthis process for each optimization cycle, thereby, constantlymaintaining optimal performance as the power plant 12 is affected byunanticipated changes in such items as load, ambient conditions, fuelcharacteristics, etc.

Turning to FIG. 6, an illustrative environment and user input device fora plant controller and control program is illustrated according to anexemplary embodiment. Though other configurations are possible, theembodiment includes a computer system 80 having a display 81, aprocessor 82, an user input device 83, and a memory 84. Aspects of thecomputer system 80 may be located at the power plant 12, while otheraspects maybe remote and connected via communications network 20. Asdiscussed, the computer system 80 may be connected to each generatingunit or other plant component 49 of the power plant 12. The power plantcomponents 49 may include gas turbine system 30, steam turbine system50, inlet conditioning system 51, HRSG duct firing system 52, and/or anysubsystems or subcomponents related thereto, or any combination thereof.The computer system 80 also may be connected to one or more sensors 46and actuators 47, as may be necessary or desired. As stated, sensors 46may be configured to sense operating conditions and parameters of thecomponents and relay signals to the computer system 80 regarding theseconditions. The computer system 80 may be configured to receive thesesignals and use them in manners described herein, which may includetransmitting signals to one or more of actuators 47. Unless otherwiserequired, however, the present invention may include embodiments thatare not configured to directly control the power plant 12 and/or tosense operating conditions. In configurations of the present inventionthat do control the power plant 12 and/or sense operating conditions,such input or control can be provided by receiving and/or transmittingsignals from/to one or more separate software or hardware systems thatmore directly interact with physical components of the power plant andits sensors and actuators. The computer system 80 may include a powerplant control program (“control program”), which makes the computersystem 80 operable to manage data in a plant controller by performingthe processes described herein.

In general, the processor 82 executes program code that defines thecontrol program, which is at least partially fixed in the memory 84.While executing program code, the processor 82 may process data, whichmay result in reading and/or writing transformed data from/to memory 84.Display 81 and input device 83 may enable a human user to interact withthe computer system 80 and/or one or more communications devices toenable a system user to communicate with computer system 80 using anytype of communications link. In embodiments, a communications network,such as networking hardware/software, may enable computer system 80 tocommunicate with other devices in and outside of a node in which it isinstalled. To this extent, the control program of the present inventionmay manage a set of interfaces that enable human and/or system users tointeract with the control program. Further, the control program, asdiscussed below, may manage (e.g., store, retrieve, create, manipulate,organize, present, etc.) data, such as control data, using any solution.

Computer system 80 may comprise one or more general purpose computingarticles of manufacture capable of executing program code, such as thecontrol programs defined herein, that is installed thereon. As usedherein, it is understood that “program code” means any collection ofinstructions, in any language, code or notation, that cause a computingdevice having an information processing capability to perform aparticular action either directly or after any combination of thefollowing: (a) conversion to another language, code or notation; (b)reproduction in a different material form; and/or (c) decompression.Additionally, computer code may include object code, source code, and/orexecutable code, and may form part of a computer program product when onat least one computer readable medium. It is understood that the term“computer readable medium” may comprise one or more of any type oftangible medium of expression, now known or later developed, from whicha copy of the program code may be perceived, reproduced, or otherwisecommunicated by a computing device. When the computer executes thecomputer program code, it becomes an apparatus for practicing theinvention, and on a general purpose microprocessor, specific logiccircuits are created by configuration of the microprocessor withcomputer code segments. A technical effect of the executableinstructions is to implement a power plant control method and/or systemand/or computer program product that uses models to enhance or augmentor optimize operating characteristics of power plants so to moreefficiently leverage the economic return of a power plant, givenanticipated ambient and/or market conditions, performance parameters,and/or life cycle cost related thereto. In addition to using currentinformation, historical and/or forecast information may be employed, anda feedback loop may be established to dynamically operate the plant moreefficiently during fluctuating conditions. The computer code of thecontrol program may be written in computer instructions executable bythe plant controller 22. To this extent, the control program executed bythe computer system 80 may be embodied as any combination of systemsoftware and/or application software. Further, the control program maybe implemented using a set of modules. In this case, a module may enablethe computer system 80 to perform a set of tasks used by controlprogram, and may be separately developed and/or implemented apart fromother portions of control program. As used herein, the term “component”means any configuration of hardware, with or without software, whichimplements the functionality described in conjunction therewith usingany solution, while the term “module” means program code that enablescomputer system to implement the actions described in conjunctiontherewith using any solution. When fixed in the memory 84 of thecomputer system 80 that includes the processor 82, a module is asubstantial portion of a component that implements the actions.Regardless, it is understood that two or more components, modules,and/or systems may share some/all of their respective hardware and/orsoftware. Further, it is understood that some of the functionalitydiscussed herein may not be implemented or additional functionality maybe included as part of the computer system 80. When the computer system80 comprises multiple computing devices, each computing device may haveonly a portion of control program fixed thereon (e.g., one or moremodules). Regardless, when the computer system 80 includes multiplecomputing devices, the computing devices may communicate over any typeof communications link. Further, while performing a process describedherein, the computer system 80 may communicate with one or more othercomputer systems using any type of communications link.

As discussed herein, the control program enables the computer system 80to implement a power plant control product and/or method. The computersystem 80 may obtain power plant control data using any solution. Forexample, computer system 80 may generate and/or be used to generatepower plant control data, retrieve power plant control data from one ormore data stores, repositories or sources, receive power plant controldata from another system or device in or outside of a power plant, plantcontroller, component controller, and/or the like. In anotherembodiment, the invention provides a method of providing a copy ofprogram code, such as for power plant control program, which mayimplement some or all of a process described herein. It is understoodthat aspects of the invention can be implemented as part of a businessmethod that performs a process described herein on a subscription,advertising, and/or fee basis. A service provider could offer toimplement a power plant control program and/or method as describedherein. In this case, the service provider can manage (e.g., create,maintain, support, etc.) a computer system, such as the computer system80, that performs a process described herein for one or more customers.

Computer models of power plants may be constructed and then used tocontrol and optimize power plant operation. Such plant models may bedynamic and iteratively updated via ongoing comparison between actual(i.e., measured) operating parameters versus those same parameters aspredicted by the plant model. In preparing and maintaining such models,instructions may be written or otherwise provided that instruct theprocessor 82 of the computer system 80 to generate a library of energysystem generating units and components (“library of components”) inresponse to user input. In some configurations, user input and thegenerated library includes properties of the component with the libraryas well as rules to generate scripts in accordance with operating andproperty values. These property values can be compiled from data storedlocally in memory 84 and/or taken from a central data repositorymaintained at a remote location. The library of components may includenon-physical components, such as economic or legal components. Examplesof economic components are fuel purchases and sales, and examples oflegal components are emission limits and credits. These non-physicalcomponents can be modeled with mathematical rules, just as componentsrepresenting physical equipment can be modeled with mathematical rules.The instructions may be configured to assemble a configuration of energysystem components from the library, as may be configured by an operator.A library of energy system components may be provided so that an usermay select from it components so to replicate an actual power plant orcreate a hypothetical one. It will be appreciated that each componentmay have several properties that may be used by the user to enterspecific values matching operating conditions of an actual orhypothetical power plant being modeled. Scripts may be generated for theassembled energy system components and their configuration. The generatescripts may include mathematical relationships within and/or among theenergy system components, including economic and/or legal components, ifused in the energy system component configuration. The computer system80 then may solve mathematical relationships and show results of thesolution on the display 81. Configurations in which signals may betransmitted from computer 80, the signals may be used to control anenergy system in accordance with the results of the solution. Otherwise,results may be displayed or printed and used for setting physicalequipment parameters and/or determining and/or using determinednonphysical parameters, such as fuel purchases and/or sales, so apreferred or optimized mode of operation is achieved. The library ofplant components may include a central repository of data representingan ongoing accumulation of data relating to how each plant componentoperates under different parameters and conditions. The centralrepository of data may be used to provide “plug data” for instances whensensor data is determined unreliable.

Turning to FIGS. 7 through 9, a more detailed discussion of the economicdispatch process is provided, including ways in which the controlsystems discussed above may be used to optimize such dispatchesprocedures from the perspective of both a power system central authorityor individual power plants participating within such systems, whicheverthe case may be. It will be appreciated that, from the perspective of acentral authority dispatcher, the objective of the economic dispatchprocess is to dynamically respond to changing variables, includingchanging load requirements or ambient conditions, while still minimizinggenerating cost within system. For the participating power plants, itwill be appreciated that, in general, the objective is to utilizeavailable capacity while minimizing generating cost so to maximizeeconomic return. Given the complexities of power systems, the process ofeconomic dispatch typically includes the frequent adjusting of load onthe participating power plants by the dispatcher. When successful, theprocess results in available power plants being operated at loads wheretheir incremental generating costs are approximately the same—whichresults in minimizing generating costs—while also observing systemconstraints, such as maximum and minimum allowable loads, systemstability, etc. It will be appreciated that accurate incremental costdata is necessary for economic dispatch to function optimally. Suchincremental cost data has primary components that include fuel cost andincremental fuel consumption. The incremental fuel consumption data isusually given as a curve of incremental heat rate versus power output.Specifically, the incremental heat rate, IHR, of a thermal generatingunit is defined as the slope of the heat rate curve, where the heat rateof the unit is the ratio of heat input plotted against electrical outputat any load. Errors in this data will result in the dispatching of unitsat loads that do not minimize total generating cost.

A number of items can introduce errors into the incremental heat ratecurves. These may be grouped into two categories. A first categoryincludes items that produce errors present at the time the data is givento the dispatcher. For example, if the data is collected by testing,errors due to instrument inaccuracy will be included in all calculationsmade with them. As discussed in more detail below, certain aspects ofthe present invention include ways of confirming sensor accuracy duringdata collection and timely identifying instances when collected data maybe unreliable due to sensor malfunction. A second category of errorsincludes items that cause data to be less accurate as time passes. Forexample, if performance of a generating unit changes due to equipmentdegradation or repair or changes in ambient conditions, the incrementalheat rate data used for dispatch will be in error until such data isupdated. One aspect of the present invention is to identify thoseparameters thermal generating units that may significantly affectincremental heat rate calculations. A knowledge of such parameters andtheir relative significance then may be used to determine how oftendispatch data should be updated to reflect true plant performance.

Errors in incremental heat rate data lead to situations where powerplants are incorrectly dispatched, which typically results in increasedgenerating cost for the power system. For example, referring to thegraph of FIG. 7, a situation is provided where the true incremental heatrate is different from the incremental heat rate that is used in thedispatch process. In dispatching the unit, the dispatch authority usesthe incremental heat rate data that is in error by “E”, as indicated,(It should be noted that FIG. 7 assumes that a power system'sincremental heat rate is not affected by the load imposed on the givenunit, which may be substantially correct if the power system is a largeone in comparison to the size of the given generating unit.) As shown,the generating unit will be dispatched L₁, which is the load where theunit and the system incremental heat rates are equal based on theinformation available. If the correct incremental heat rate informationwere used, the unit would be dispatched at L₂, the load where the trueincremental heat rate of the plant equals the power system's incrementalheat rate. As will be appreciated, the error results in theunderutilization of the power plant. In cases where the alternative istrue, i.e., where the positioning of the incorrect incremental heat rateplot relative to the true incremental heat rate plot is reversed, theerror results in the unit being overcommitted, which may require it tooperate inefficiently to satisfy its dispatched load commitment. Fromthe perspective of the central dispatch authority of the power system,it will be appreciated that reducing errors in the data used in thedispatch process will reduce total system fuel costs, increase systemefficiency, and/or decrease the risk of not meeting load requirements.For the operators of power plants within the system, reducing sucherrors should promote full utilization of the plant and improve economicreturn.

FIGS. 8 and 9, respectively, illustrate a schematic diagram of a plantcontroller 22 and a flow diagram 169 of a control method pursuant toaspects of the present invention. In these examples, methods areprovided that illustrate economic optimization within a power systemthat uses economic dispatch to distribute load among possible providers.The fundamental process of economic dispatch is one that may be employedin different ways and between any two levels defined within the layeredhierarchy common to many power systems. In one instance, for example,the economic dispatch process may be used as part of a competitiveprocess by which a central government authority or industry cooperativeassociation of portions load among several competing companies.Alternatively, the same principles of economic dispatch may be used toapportion load among commonly owned power plants so to minimizegenerating costs for the owner of the plants. It may also be used at theplant level as a way for an operator or plant controller to apportionits load requirements among the different local generating units thatare available to it. It will be appreciated that, unless otherwisestated, the systems and methods of the present invention are generallyapplicable to any of these possible manifestations of the economicdispatch process.

In general, the dispatch process seeks to minimize generating costwithin a power system via the creation of a dispatch schedule in whichthe incremental generating costs for each participating power plant orgenerating unit is approximately the same. As will be appreciated,several terms are often used to describe the economic dispatch process,and so will be defined as follows. A “prediction horizon” is apredefined period of time over which optimization is to be performed.For example, a typical prediction horizon may be from a few hours to afew days. An “interval” within the prediction horizon is a predefinedtime resolution of optimization, i.e., the aforementioned “optimizationcycle”, which describes how often optimization is to be performed duringthe prediction horizon. For example, a typical time interval for anoptimization cycle may be from several seconds to several minutesFinally, a “prediction length” is the number of time intervals for whichoptimization is to be performed, and may be obtained by dividing theprediction horizon by the time interval. Thus, for a 12-hour predictionhorizon and a 5-minute time interval, a prediction length is 144 timeintervals.

Aspects of the present invention provide methods of control and/orcontrollers for power plants, as well as methods and systems foroptimizing performance, cost-effectiveness, and efficiency. For example,according to the present invention, a minimum variable operating costmay be achieved for a thermal generating unit or power plant thatbalances variable performance characteristics and cost parameters (i.e.,fuel cost, ambient conditions, market conditions, etc.) with life-cyclecost (i.e., variable operation and its effect on maintenance schedules,part replacement, etc.). By varying one or more parameters of a thermalgenerating unit taking such factors into account, more economicaladvantage may be taken of the unit over its useful life. For example, inpower plants that include a gas turbine, firing temperature may bevaried to provide a desired load level more economically based onoperating profile, ambient conditions, market conditions, forecasts,power plant performance, and/or other factors. As a result, the disposalof parts with residual hours-based life remaining in starts-limitedunits may be reduced. Further, a power plant control system thatincludes a feedback loop updated with substantially real-time data fromsensors that are regularly tested and confirmed as operating correctlywill allow further plant optimization. That is, according to certainembodiments of the present invention, by introducing a real-timefeedback loop between the power plant control system and dispatchauthority, target load and unit commitment may be based on highlyaccurate offer curves that are constructed based on real-time engineperformance parameters.

FIG. 8 illustrates a schematic design of an exemplary the plantcontroller 22 according to aspects of the present invention. It will beappreciated that the plant controller 22 may be particularly well-suitedfor implementing method 169 of FIG. 9. Because of this, FIGS. 8 and 9will be discussed together, though it will be appreciated that each mayhave aspects applicable to more general usage. The power system 10represented in FIG. 8 includes a “power plant 12 a”, to which the plantcontroller 22 is dedicated, as well as “other power plants 12 b”, whichmay represent power plants within the power system that compete againstpower plant 12 a. As illustrated, the power system 10 also includes adispatch authority 24 that, through a dedicated system controller 25,manages the dispatch process between all participating power plants 12a, 12 b within the system.

The power plant 12 a may include numerous sensors 46 and actuators 47 bywhich the plant controller 22 monitors operating conditions and controlsthe plant's operation. The plant controller 22 may communicate withnumerous data resources 26, which may be located remotely to it andaccessible over a communications network and/or contained locally andaccessible over a local network. As illustrated, the schematicrepresentation of the plant controller 22 includes several subsystemswhich have been delineated from each other by the several boxes. Thesesubsystems or “boxes” have been separated mostly by function so toassist in description. However, it will be appreciated that separatedboxes may or may not represent individual chips or processors or otherindividual hardware elements, and may or may not represent separatedsections of computer program code executed within the plant controller,unless otherwise stated. Similarly, while the method 169 is broken intotwo major sections or blocks, this is for convenience and to assist withdescription. It will be appreciated that any or all of the separateboxes shown in FIG. 8 may be combined into one or more sections in theplant controller 22, as may any or all of the separate blocks or stepsshown in FIG. 9.

The method 169 of FIG. 9 may begin, for example, with a control section170 that receives or gathers present information and data for use (atstep 171), which may include market data, operating data, and/or ambientdata. Within the plant controller 22, a corresponding control module 110may be arranged to request/receive this type of data from data resources26 or any other suitable source. Control module 110 may also beconfigured to receive a target load 128 from dispatch authority 24(though on an initial run, such a target load may not be available, anda predefined initial target load may be used). Ambient data may bereceived from remote or local data repositories and/or forecastservices, and may be included as a component of data resources 26.Ambient data also may be gathered via ambient sensors deployed aroundpower plant 12 a, as well as received via a communication link with thedispatch authority 24. According to aspects of the present invention,ambient data includes historical, present, and/or forecast data thatdescribe ambient conditions for power plant 12 a, which, for example,may include air temperature, relative humidity, pressure, etc. Marketdata may be received from remote or local data repositories and/orforecast services, and may be included as a component of data resources26. Market data may also be received via a communication link withdispatch authority 24. According to aspects of the present invention,market data includes historical, present, and/or forecast data thatdescribe market conditions for power plant 12 a, which, for example,includes energy sale price, fuel cost, labor cost, etc. Operating dataalso may be received from data repositories, and/or forecast services,and may be included as a component of data resources 26. Operating datamay include data collected from multiple sensors 46 deployed within thepower plant 12 and its plant components 49 that measure physicalparameters relating to plant operation. Operating data may includehistorical, present, and/or forecast data, as well as a variety ofprocess inputs and outputs.

As seen in FIG. 9, an initial setpoint for the power plant 12 may bedetermined, such as with a controls model 111 in the plant controller 22of FIG. 8. For example, the controls model 111 may be configured to usethermodynamic and/or physical details of the power plant 12 andadditional information, such as ambient data or market data or processdata, to determine a value of an operating parameter for the power plant12 (at step 172 of FIG. 9). In one instance, for example, the value ofan operating parameter may be a value that would be required to achievepower output sufficient to meet a target load. The determined value maybe used as an initial setpoint for the respective operating parameter ofthe power plant 12. (also step 172 of FIG. 9). It will be appreciatedthat examples of such operating parameters may include: fuel flow rate,firing temperature, a position for inlet guide vanes (if guide vanes arepresent), a steam pressure, a steam temperature, and a steam flow rate.A performance indicator then may be determined (at step 173 of FIG. 9)by using a performance model 112 of the plant controller 22. Theperformance indicator may provide an operating characteristic, such asefficiency, of the power plant 12. The performance model 112 may beconfigured to use thermodynamic and/or physical details of the powerplant 12, as well as the setpoints determined by controls model 111, soto determine a value of an operating characteristic of the power plant12. The performance model 112 may be configured to take into accountadditional information, such as ambient conditions, market conditions,process conditions, and/or other relevant information.

In addition, according to certain aspects of the present invention, anestimate may be determined of a life cycle cost (LCC) of the power plant12 (at step 174 of FIG. 9), such as with a LCC model 113 that isincluded in the plant controller 22 of FIG. 8. The LCC model 113, whichmay be a computer program or the like, may be configured to use physicaland/or cost information about the power plant 12, as well as setpointsfrom controls model 111 to determine an estimated life cycle cost ofpower plant 12. Life cycle cost may include, for example, a total cost,a maintenance cost, and/or an operating cost of power plant 12 over itsservice life. The LCC model 113 may additionally be configured to takeinto account the results of performance model 112 for enhanced accuracy.The LCC model 113 may therefore use the determined setpoints of controlsmodel 111 and the operating characteristic from the performance model112, as well as other information, as desired, to estimate the servicelife of the power plant 12, as well as how much it may cost to operateand/or maintain the power plant 12 during its service life. As notedabove, the service life of a power plant may be expressed in hours ofoperation and/or number of starts, and a given power plant has anexpected service life that may be provided by a manufacturer of thepower plant. Thus, predefined values of expected service life may beused at least as a starting point for LCC model 113, and/or anenhancement module 114.

Using information from other embodiments of the invention, such asresults from determining an initial setpoint, a performance indicator,and an estimated life cycle, an optimization problem may be solved forthe power plant 12 (at step 175) as described below. Such anoptimization problem may include a plurality of equations and variables,depending on a depth of analysis desired, and may include an objectivefunction, which in embodiments may be a LCC-based objective function.The solution may include providing an enhanced or augmented operatingparameter of the power plant 12, such as, for example, by minimizing aLCC-based objective function (also step 175). In embodiments, thesolution of the optimization problem may be performed by an enhancementmodule 114 of the plant controller 22 of FIG. 8.

As is known from optimization theory, an objective function represents acharacteristic or parameter to be optimized and may take into accountmany variables and/or parameters, depending on how the optimizationproblem is defined. In an optimization problem, an objective functionmay be maximized or minimized, depending on the particular problemand/or the parameter represented by the objective function. For example,as indicated above, an objective function expressing LCC according toembodiments would be minimized to produce at least one operatingparameter that may be used to run the power plant 12 so as to keep LCCas low as feasible. An optimization problem for the power plant 12, orat least an objective function, may take into account such factors aspower plant characteristics, site parameters, customer specifications,results from controls model 111, performance model 112, and/or LCC model113, ambient condition, market condition, and/or process condition, aswell as any additional information that might be suitable and/ordesired. Such factors may be gathered into terms of an objectivefunction, so that, for example, a LCC-based objective function includesmaintenance cost and operation cost represent over time, where time is aprediction horizon based on an estimated component service life. It willbe appreciated that complex objective functions and/or optimizationproblems may be used in implementations of the present invention, aseach may include many or all of the various functions and/or factorsthat are described herein.

Maintenance cost, for example, may be determined by modeling parts ofthe power plant 12 to estimate wear based on various parameters, such asthose already discussed. It will be appreciated that any part of thepower plant 12 may be modeled for these purposes. In a practicalapplication, however, the parts associated with fewer, larger portions,or fewer, select portions of the power plant 12 might be modeled, and/orconstants or plug values might be used for some parts instead ofmodeling. Whatever level of detail is employed, minimization of such anLCC-based objective function is part of an optimization problem that mayvary for a given power plant as a result of many factors, such as thoseprovided above, and may include at least one enhanced or augmentedoperating parameter of the power plant 12, such as in accordance withminimizing LCC. In addition, those skilled in the art will recognizethat at least one constraint may be imposed upon the optimizationproblem, such as a predefined up time and/or down time, a predefinedupper and/or lower temperature at various locations in the power plant12, a predefined torque, a predefined power output, and/or otherconstraints as may be desired and/or appropriate. Unless otherwisestated, it is within the purview of those skilled in the art todetermine what constraints should be applied and in what manner for agiven optimization problem. Further, those skilled in the art willrecognize situations in which additional optimization theory techniquesmay be applied, such as adding a slack variable to allow a feasiblesolution to the optimization problem.

Known techniques may be employed, such as by enhancement module 114(FIG. 8), to solve an optimization problem for operation of the powerplant 12. For example, an integer programming, a linear, a mixed integerlinear, a mixed integer nonlinear, and/or another technique may be usedas may be suitable and/or desired. In addition, as seen in the exampleobjective function, the optimization problem may be solved over aprediction horizon, providing an array of values for at least oneoperating parameter of the power plant 12. While enhancement oraugmentation may be performed over a relatively short predictionhorizon, such as 24 hours or even on the order of minutes, enhancementmodule 114 (FIG. 8) may employ a longer prediction horizon, such as upto an estimated service life of the power plant 12, depending on a depthof analysis desired. In embodiments, initial setpoints determined, suchas by controls model 111 (FIG. 8), may be adjusted responsive to and/oras part of the solution of the optimization problem to yield an enhancedor augmented or optimized setpoint. In addition, iteration may be usedwith determining an initial setpoint, determining a value of aperformance indicator, determining an estimated LCC cost, and enhancingor augmenting (at steps 172-175 of FIG. 9) to refine results and/orbetter enhance or augment control setpoints of the power plant 12.

As will be described, an offer curve section 180 may generate an offercurve or set of offer curves, an example of which was shown previous inrelation to FIG. 7. In the plant controller 22, control information 115from control module 110 and/or data resources 26 may be received (atstep 181 of FIG. 9) by an offer curve module 120. According to certainembodiments, control information 115 includes: control setpoints,performance, ambient conditions, and/or market conditions. Thisinformation may also be known as “as run” information. In addition, anambient condition forecast 121 and/or market condition forecast 122 maybe received (at step 182). According to certain embodiments, a database123 may be included and may store current information, “as run”information, and/or historical information locally, including any or allof ambient conditions, market conditions, power plant performanceinformation, offer curves, control setpoints, and/or any otherinformation which may be suitable. Database 123 may be used to provideinformation to simulate operation of the power plant 12 (at step 183),such as with an offline model 124 of the power plant 12.

Offline model 124 may include a model similar to controls model 111, butmay also include additional modeling information. For example, offlinemodel 124 may incorporate portions or entireties of controls model 111,performance model 112, LCC model 113, and/or additional modelinginformation. By running offline model 124 with setpoints and/orinformation from enhancing or augmenting LCC, output of offline model124 may be used to determine estimated values for cost of powerproduction for each time interval in a prediction horizon and forvarious values of power output of the power plant 12 to generate one ormore offer curves 125 (at step 184) which may be sent or otherwiseprovided to dispatch authority 24 (at step 185). Offline model 124 mayuse any suitable information, such as historical, current, and/orforecast information, in determining estimated operating costs and/orconditions of the power plant 12. In addition, offline model 124 inembodiments may be tuned (at step 186), such as by a model tuning module126. Tuning may include; for example, periodically adjusting parametersfor offline model 124 based on information received and/or provided byother parts of the plant controller 22 to better reflect actualoperation of the power plant 12 so as to better simulate operation ofthe power plant 12. Thus, for a given set of operating parameters, ifplant controller 12 observes an actual process condition that differsfrom what offline model 124 had predicted, plant controller 12 maychange offline model 124 accordingly.

In addition to the offer curves 125 from the power plant 12 a, asillustrated, dispatch authority 24 may receive offer curves 125 fromother power plants 12 b under its control. Dispatch authority 24 mayassess the offer curves 125 and may generate a dispatch schedule toaccommodate load on power system 10. Dispatch authority 24 mayadditionally take into account forecasted ambient conditions, a loadforecast and/or other information as may be appropriate and/or desired,which it may receive from various local or remote data resources 26 towhich it has access. As illustrated in, the dispatch schedule producedby dispatch authority 24 includes a control signal for the power plant12 that includes a target load 128, to which the plant controller 22 mayrespond as described above.

It will be appreciated that the inclusion of life-cycle costsconsiderations, as described herein, may serve to increase the scope andaccuracy of the plant models used in the optimization process and, indoing this, enable enhancements to the procedure. Offer curves 125, asdescribed above, may represent variable cost (measured in dollars permegawatt-hour versus power plant output in megawatts). Offer curves 125may include an incremental variable cost offer curve and an averagevariable cost offer curve. As can be seen, embodiments of the presentinvention may provide accurate assessments of variable cost via theirgenerated offer curves 125. Using embodiments of the present invention,incremental variable cost offer curves have been shown to predict veryclosely actual incremental variable cost curves, while average variablecost offer curve have been shown to predict very closely actual averagevariable cost curves. The accuracy of the offer curves generated byembodiments of the present invention indicates that the various modelsused in the plant controller 22 of FIG. 8 provides a suitablyrepresentative model for the purposes outlined.

Turning now to the FIGS. 10 through 12, other aspects of the presentinvention are described with reference to and inclusive of certainsystems and methods provided above. FIG. 10 is a data flow diagramdemonstrating an architecture for a plant optimization system 200 thatmay be used in a combined-cycle power plant having gas and steam turbinesystems. In the embodiment provided, a system 200 includes monitoringand control instruments 202, 204, such as the sensors and actuatorsdiscussed above, associated with each of the gas turbine (202) and thesteam turbine systems (204). Each of the monitoring and controlinstruments 202, 204 may transmit signals indicative of measuredoperating parameters to a plant controller 208. The plant controller 208receives the signals, processes the signals in accordance withpredetermined algorithms, and transmits control signals to monitoringand control instruments 202, 204 to affect changes to plant operations.

The plant controller 208 interfaces with a data acquisition module 210.The data acquisition model 210 may be communicatively coupled to adatabase/historian 212 that maintains archival data for future referenceand analysis. A heat balance module 214 may receive data from dataacquisition model 210 and database/historian 212 as requested to processalgorithms that tunes a mass and energy balance model of the power plantto match measured data as closely as possible. Discrepancies between themodel and the measured data may indicate errors in the data. As will beappreciated, a performance module 216 may use plant equipment models topredict the expected performance of major plant components andequipment. The difference between expected and current performance mayrepresent degradation of the condition of plant equipment, parts, andcomponents, such as, but, not limited to fouling, scaling corrosion, andbreakage. According to aspects of the present invention, the performancemodule 216 may track degradation over time so that performance problemshaving the most significant effect on plant performance are identified.

As illustrated, an optimizer module 218 may be included. The optimizermodule 218 may include a methodology for optimizing an economic dispatchof the plant. For example, according to embodiments, the power plant maybe dispatched based on heat rate or incremental heat rate pursuant tothe assumption that heat rate is equivalent to monetary resources. In analternative scenario, in which the power plant includes an additionalmanufacturing process (not shown) for which steam is used directly(i.e., where the steam produced may be diverted from power generation inthe steam turbine to another manufacturing use), it will be appreciatedthat the optimizer module 218 may solve an optimization problem whereina component with a higher heat rate may be dispatched. For example, incertain situations, a demand for steam may outpace a demand forelectricity or the electrical output may be constrained by electricalsystem requirements. In such cases, dispatching a lower efficiency gasturbine engine may allow greater heat to be recovered without raisingelectrical output in excess of a limit In such scenarios, thedispatching of the component with a higher heat rate is the economicallyoptimized alternative.

The optimizer module 218 may be selectable between an online (automatic)and an offline (manual) mode. In the online mode, the optimizer 218automatically computes current plant economic parameters such as cost ofelectricity generated, incremental cost at each level of generation,cost of process steam, and plant operating profit on a predeterminedperiodicity, for example, in real-time or once every five minutes. Anoffline mode may be used to simulate steady-state performance, analyze“what-if” scenarios, analyze budget and upgrade options, and predictcurrent power generation capability, target heat rate, correction ofcurrent plant operation to guarantee conditions, impact of operationalconstraints and maintenance actions, and fuel consumption. The optimizer218 calculates a profit optimized output for the power plant based onreal-time economic cost data, output prices, load levels, and equipmentdegradation, rather than an output based on efficiency by combiningplant heat balances with a plant financial model. The optimizer 218 maybe tuned to match the degradation of each component individually, andmay produce an advisory output 220 and/or may produce a closed feedbackloop control output 222. Advisory output 220 recommends to operatorswhere to set controllable parameters of the power plant so to optimizeeach plant component to facilitate maximizing profitability. In theexemplary embodiment, advisory output 220 is a computer display screencommunicatively coupled to a computer executing optimizer module 218. Inan alternative embodiment, advisory output is a remote workstationdisplay screen wherein the workstation accesses the optimizer module 218through a network. Closed feedback loop control output 222 may receivedata from optimizer module 218 and calculates optimized set pointsand/or bias settings for the modules of system 200 to implementreal-time feedback control.

FIG. 11 is a simplified block diagram of a real-time thermal power plantoptimization system 230 that, according to aspects of the presentinvention, includes a server system 231, and a plurality of clientsub-systems, also referred to as client systems 234, communicativelycoupled to the server system 231. As used herein, real-time refers tooutcomes occurring at a substantially short period after a change in theinputs affect the outcome, for example, computational calculations. Theperiod represents the amount of time between each iteration of aregularly repeated task. Such repeated tasks may be referred to hereinas periodic tasks or cycles. The time period is a design parameter ofthe real-time system that may be selected based on the importance of theoutcome and/or the capability of the system implementing processing ofthe inputs to generate the outcome. Additionally, events occurring inreal-time, occur without substantial intentional delay. In the exemplaryembodiment, calculations may be updated in real-time with a periodicityof one minute or less. Client systems 234 may be computers that includea web browser, such that server system 231 is accessible to clientsystems 234 via the Internet or some other network. Client systems 234may be interconnected to the internet through many interfaces. Clientsystems 234 could be any device capable of interconnecting to theinternet. A database server 236 is connected to a database 239containing information regarding a plurality of matters, as describedbelow in greater detail. In one embodiment, a centralized database 239,which includes aspects of data resources 26 discussed above, is storedon server system 231 and can be accessed by potential users at one ofclient systems 234 by logging onto server system 231 through the clientsystems 234. In an alternative embodiment database 239 is storedremotely from server system 231 and may be non-centralized.

According to aspects of the present invention, certain of the controlmethods discussed above may be developed for use in conjunction withsystem diagrams of FIGS. 10 and 11. For example, one method includessimulating power plant performance using a plant performance module of asoftware code segment that receives power plant monitoring instrumentdata. The data may be received through a network from a plant controlleror a database/historian software program executing on a server. Anyadditional plant components, such as an inlet conditioning system or aHRSG duct firing system, may be simulated in a manner similar to thatused to simulate power plant performance. Determining the performance ofeach plant component in the same manner allows the overall power plantto be treated as a single plant to determine optimize setpoints for thepower plant rather than determining such setpoints for each componentseparately. Measurable quantities for each plant component may beparameterized so to express output or power plant efficiency on acomponent by component basis. Parameterizing plant equipment and plantperformance includes calculating efficiency for components, such as, butnot limited to, a gas turbine compressor, a gas turbine, a heat recoverysteam generator (HRSG), a draft fan, a cooling tower, a condenser, afeed water heater, an evaporator, a flash tank, etc. Similarly, it willbe appreciated that heat-rate and performance calculations may beparameterized and the resulting simultaneous equations solved inreal-time, such that calculated results are available withoutintentional delay from the time each parameter was sampled. Solvingparameterized simultaneous equations and constraints may also includedetermining a current heat balance for the power plant, determining anexpected performance using present constraints on the operation of thepower plant, such as, but not limited to spinning reserve requirements,electrical system demand, maintenance activities, freshwater demand, andcomponent outages. Solving parameterized equations and constraints mayalso include determining parameters to adjust to modify the current heatbalance such that a future heat balance equals the determined expectedperformance. In an alternative embodiment, solving parameterizedsimultaneous equations and constraints includes determining inletconditions to the power plant, predicting an output of the power plantbased on the determined inlet conditions and a predetermined model ofthe power plant, determining a current output of the power plant,comparing the predicted output to the determined output, and adjustingplant parameters until the determined output equals the predictedoutput. In exemplary embodiments, the method also includes correlatingcontrollable plant parameters, plant equipment, and plant performanceusing parameterized equations, defining the objective of theoptimization using an objective function that includes minimizing theheat rate of the power plant and/or maximizing the profit of the powerplant, and defining the physically possible range of operation of eachindividual piece of equipment, and/or overall limits using constraintswherein the overall limits include maximum power production, maximumfuel consumption, etc.

FIG. 12 a flow chart of an exemplary method 250 for solvingparameterized simultaneous equations and constraints in accordance withthe present invention. The method 250 includes determining (at 252) acurrent heat balance for the power plant, determining (at 254) anexpected performance using current constraints on operation, anddetermining (at 256) parameters to adjust so to modify the current heatbalance such that a future heat balance equals the determined expectedperformance. The method 250 also includes determining 258 inletconditions to the power plant, predicting 260 an output of the powerplant based on the determined inlet conditions and a predetermined modelof the power plant, determining 262 a current output of the power plant,comparing 264 the predicted output to the determined output, andadjusting 266 plant parameters until the determined output equals thepredicted output. It will be appreciated that the described method, andsystems discussed in relation to the FIGS. 10 and 11, provide acost-effective and reliable means for optimizing combined-cycle powerplants.

Turning now to FIGS. 13 through 16, attention will be paid to theseveral flow diagrams and system configurations that illustrate controlmethodology according to certain aspects of the present invention. Ingeneral, according to an example embodiment, a control system for athermal generating unit, such as the gas turbine system, or power plantmay include first and second instances of a model that models theoperation of the turbine, such as by utilizing physics-based models ormathematically modeling (e.g., transfer functions, etc.). The firstmodel (which may also be referred to as the “primary model”) may providepresent operating parameters of the gas turbine system, which describethe turbines mode of operation and the operating conditions thatcorrespond to it. As used herein, “parameters” refer to items that canbe used to define the operating conditions of the turbine, such as, butnot limited to, temperatures, pressures, gas flows at defined locationsin the turbine, and compressor, combustor, and turbine efficiencylevels, etc. Performance parameters may also be referred to as “modelcorrection factors,” referring to factors used to adjust the first orsecond models to reflect the operation of the turbine. Inputs to thefirst model may be sensed or measured and provided by an operator. Inaddition to current performance parameters, the method of the presentinvention may include receiving or otherwise obtaining information onexternal factors or disturbance variables, such as ambient conditions,that may affect the present or future operation of the gas turbinesystem.

The second model (also referred to as a “secondary model” or a“predictive model”) is generated to identify or predict one or moreoperating parameters, such as controlled variables, of the gas turbinesystem, taking into consideration the present operating parameters, suchas manipulated variables, and the one or more disturbance variables.Example operating parameters of the turbine include, but are not limitedto, actual turbine operating conditions, such as, exhaust temperature,turbine output, compressor pressure ratios, heat rate, emissions, fuelconsumption, expected revenues, and the like. Therefore, this second orpredictive model may be utilized to indicate or predict turbine behaviorat certain operating set points, performance objectives, or operatingconditions that differ from present operating conditions. As usedherein, the term “model” refers generally to the act of modeling,simulating, predicting, or indicating based on the output of the model.It is appreciated that, while the term “second model” is utilizedherein, in some instances there may be no difference between theformulation of the first and second models, such that the “second model”represents running the first model with adjusted parameters oradditional or different input.

Accordingly, by modeling the turbine operating behavior utilizing thesecond or predictive model that considers external factors and/ordifferent operating conditions, turbine control can be adjusted to moreefficiently operate under these different operating conditions or inlight of the unanticipated external factors. This system thereforeallows automated turbine control based on modeled behavior and operatingcharacteristics. In addition, the described modeling system allowscreating operator specified scenarios, inputs, operating points,operating objectives, and/or operating conditions to predict turbinebehavior and operating characteristics at these operator specifiedconditions. Predicting such hypothetical scenarios allows operators tomake more informed control and operating decisions, such as scheduling,loading, turn-down, etc. As used herein, the term “operating points”refers generally to operating points, conditions, and/or objectives, andis not intended to be limiting. Thus, an operating point may refer to anobjective or setpoint, such as base load, turndown point, peak fire, andthe like.

One example use of the described turbine modeling system includesadjusting turbine operation to satisfy grid compliance requirementswhile still operating at the most efficient levels. For example,regional grid authorities typically prescribe requirements that powergeneration plants be able to support a grid during frequency upsets.Supporting the grid during upsets involves increasing or decreasingturbine load under certain conditions, depending upon the grid state.For example, during an upset, a power plant is expected to increase itspower generation output (e.g., by as much as 2%) to compensate for othersupply deficiencies. Therefore, turbine operation typically constrainsthe base load point to allow for the turbine to be operated at amargined output level (also referred to as the “reserved margin”) sothat the increased load, if necessary, can be provided without incurringthe additional maintenance factor associated with over firing. As oneexample, the reserved margin may be 98% of what base load wouldtypically be, thus allowing increasing load to accommodate gridrequirements (e.g., increasing 2%) without exceeding the 100% base load.However, unanticipated external factors, such as temperature, humidity,or pressure, can adversely impact turbine efficiency. As a day heats up,a turbine may not have that 2% reserve that it needs because heat hascaused the turbine to operate less efficiently and the turbine cannotreach that 100% load as originally planned for. To compensate,conventional heat-rate curves cause operating the turbine in a moreefficient state throughout the entire day in light of the possiblemachine efficiency loss (e.g., at 96%, etc.). The turbine modelingsystem described herein, however, allows modeling turbine behavior inreal-time according to the current external factors (e.g., temperature,humidity, pressure, etc.), and thus controlling turbine operation tomost efficiently operate given the current ambient conditions.Similarly, future turbine behavior can be predicted, such as to predictturbine behavior responsive to a day's heat fluctuation, allowing forturbine operation planning to achieve the most efficient andeconomically viable operation. As another example, power generationplants typically make decisions whether to shut gas turbines down atnight or to simply reduce output levels (e.g., turn down). Turbineoperating characteristics, such as emissions, exhaust temperature, andthe like, impact this decision. Utilizing the turbine modeling systemdescribed herein, decisions can be made on a more intelligent basis,either before-hand or in real-time or near real-time. External factorsand expected turbine operating parameters can be supplied to the secondmodel to determine what the turbine operating characteristics would be.Thus, the modeled characteristics may be utilized to determine whether aturbine should be shut down or turned down, considering thesecharacteristics (e.g., efficiency, emissions, cost, etc.).

As yet another example, a turbine modeling system may be utilized toevaluate the benefit of performing turbine maintenance at a given time.The turbine modeling system of the present invention may be utilized tomodel the operating characteristics of the turbine at its currentcapabilities based on current performance parameters. Then, an operatorspecified scenario can be generated that models the operatingcharacteristics of the turbine if maintenance is performed (e.g.,improving the performance parameter values to show an expectedperformance boost). For example, as turbines degrade over time, theperformance parameters reflect machine degradation. In some instances,maintenance can be performed to improve those performance parametersand, thus, the operating characteristics of the turbine. By modeling orpredicting the improved operating characteristics, a cost-benefitanalysis can be performed to compare the benefit gained by performingthe maintenance against the costs incurred.

FIG. 13 illustrates an exemplary system 300 that may be used to modelturbine operating behavior. According to this embodiment, a power plant302 is provided that includes a gas turbine having a compressor and acombustor. An inlet duct to the compressor feeds ambient air andpossibly injected water to the compressor. The configuration of theinlet duct contributes to a pressure loss of ambient air flowing intothe compressor. An exhaust duct for the power plant 302 directscombustion gases from the outlet of the power plant 302 through, forexample, emission control and sound absorbing devices. The amount ofinlet pressure loss and back pressure may vary over time due to theaddition of components to the inlet and exhaust ducts, and due toclogging of the inlet and exhaust ducts.

The operation of the power plant 302 may be monitored by one or moresensors detecting one or more observable conditions, or operating orperformance parameters, of the power plant 302. In addition, externalfactors, such as the ambient environment can be measured by one or moresensors. In many instances, two or three redundant sensors may measurethe same parameter. For example, groups of redundant temperature sensorsmay monitor ambient temperature surrounding the power plant 302, thecompressor discharge temperature, the turbine exhaust gas temperature,as well as other temperatures through the power plant 302. Similarly,groups of redundant pressure sensors may monitor the ambient pressure,and the static and dynamic pressure levels at the compressor inlet andoutlet, the turbine exhaust, and other locations through the engine.Groups of redundant humidity sensors may measure ambient humidity in theinlet duct of the compressor. Groups of redundant sensors may alsocomprise flow sensors, speed sensors, flame detector sensors, valveposition sensors, guide vane angle sensors, or the like that sensevarious parameters pertinent to the operation of power plant 302. A fuelcontrol system may regulate the fuel flowing from a fuel supply to thecombustor. The fuel controller may also select the type of fuel for thecombustor.

As stated, “operating parameters” refer to items that can be used todefine the operating conditions of the turbine system, such astemperatures, pressures, compressor pressure ratio, gas flows at definedlocations in the turbine, load setpoint, firing temperature, as well asone or more conditions corresponding to the level of turbine orcompressor degradation and/or the level of turbine or compressorefficiency. Some parameters are measured directly. Other parameters areestimated by the turbine models or are indirectly known. Still otherparameters may represent hypothetical or future conditions and may bedefined by the plant operator. The measured and estimated parameters maybe used to represent a given turbine operating states. As used herein,“performance indicators” are operating parameters derived from thevalues of certain measured operating parameters, and represent aperformance criteria for the operation of the power plant over a definedperiod. For example, performance indicators include heat rate, outputlevel, etc.

As illustrated in FIG. 13, the system 300 includes one or morecontrollers 303 a, 303 b, which may each be a computer system having oneor more processors that execute programs to control the operation of apower plant or generating unit 302. Although FIG. 13 illustrates twocontrollers, it is appreciated that a single controller 303 by beprovided. According to a preferred embodiment, multiple controllers maybe included so to provide redundant and/or distributed processing. Thecontrol actions may depend on, for example, sensor inputs orinstructions from plant operators. The programs executed by thecontroller 303 may include scheduling algorithms, such as those forregulating fuel flow to the combustor, managing grid compliance,turndown, etc. The commands generated by the controller 303 can causeactuators on the turbine to, for example, adjust valves between the fuelsupply and combustors so to regulate fuel flow, splits and type of fuel.Actuators may adjust inlet guide vanes on the compressor, or activateother control setpoints on the turbine. It will be appreciated that thecontroller 303 may be used to generate the first and/or the secondmodels, as described herein, in addition to facilitating control of thepower plant. The controller 303 may receive operator and/or presentmodeled output (or any other system output.) As described previously,the controller 303 may include memory that stores programmed logic(e.g., software) and may store data, such as sensed operatingparameters, modeled operating parameters, operating boundaries andgoals, operating profiles, and the like. A processor may utilize theoperating system to execute the programmed logic, and in doing so, alsomay utilize data stored thereon. Users may interface with the controller303 via at least one user interface device. The controller 303 may be incommunication with the power plant online while it operates, as well asin communication with the power plant offline while it is not operating,via an I/O interface. It will be appreciated that one or more of thecontrollers 303 may carry out the execution of the model-based controlsystem described herein, which may include but not be limited to:sensing, modeling, and/or receiving operating parameters and performanceparameters; generating a first power plant model reflecting currentturbine operation; sensing, modeling, and/or receiving external factorinformation; receiving operator input, such as performance objectives,and other variables; generating a second power plant model reflectingoperation in light of the additional data supplied; controlling presentor future turbine operation; and/or presenting modeled operatingcharacteristics. Additionally, it should be appreciated that otherexternal devices or multiple other power plants or generating units maybe in communication with the controller 303 via I/O interfaces. Thecontroller 303 may be located remotely with respect to the power plantit controls. Further, the controller 303 and the programmed logicimplemented thereby may include software, hardware, firmware, or anycombination thereof.

The first controller 303 a (which, as stated, may be the same ordifferent controller as the second controller 303 b) may be operable soto model the power plant 302 by a first or primary model 305, includingmodeling the turbine's current performance parameters. The secondcontroller 303 b may be operable to model turbine operatingcharacteristics under different conditions via a second or predictivemodel 306. The first model 305 and the second model 306 may each be anarrangement of one or more mathematical representations of the turbinebehavior. Each of these representations may rely on input values togenerate an estimated value of a modeled operating parameter. In somecircumstances, the mathematical representations may generate a surrogateoperating parameter value that may be used in circumstances where ameasured parameter value is not available. The first model 305 may thenbe utilized to provide a foundation and/or input to the second model 306for determining turbine operating characteristics based on the currentperformance parameters of the power plant 302 and any other factors,such as external factors, operator supplied commands or conditions,and/or adjusted operating states. As described above, it is appreciatedthat “the second model 306” may simply be an instance of the same modelas the first model 305 that considers additional or different inputs,such as external factors, different operating points, so to modeldifferent performance parameters or turbine behavior in light of thedifferent inputs. The system 301 may further include an interface 307.

With continued reference to FIG. 13, a brief description of theinterrelation between the system components is provided. As described,the first or primary model 305 models current performance parameters 308of the power plant 302. These current performance parameters 308 mayinclude, but are not limited to, conditions corresponding to the levelof turbine degradation, conditions corresponding to the level of turbineefficiency (e.g., the heat rate or fuel to power output ratio), inletguide vane angles, amount of fuel flow, turbine rotational speed,compressor inlet pressure and temperature, compressor exit pressure andtemperature, turbine exhaust temperature, generator power output,compressor airflow, combustor fuel/air ratio, firing temperature(turbine inlet), combustor flame temperature, fuel system pressureratios, and acoustic characteristics. Some of these performanceparameters 308 may be measured or sensed directly from the turbineoperation and some may be modeled based on other measured or sensedparameters. The performance parameters may be provided by the firstmodel 305 and/or may be provided generally by the controller, such as ifsensed and/or measured by the controller. Upon generating the firstmodel 305, the performance parameters 308 (which are intended to referto any turbine behavior provided by the model) are provided forgenerating the second or predictive model 306. Other variables 309 maybe provided to the second model 306, depending upon the its intendeduse. For example, the other variables may include external factors, suchas ambient conditions, that generally are uncontrollable and simply haveto be accommodated for. In addition, the other variables 309 may includea controller specified scenario or operating point (e.g., a turbineoperating point generated by or otherwise provided via the controller303, such as turbine control based on the first model 305, etc.),measured inputs, which may be some or all of the same measured inputs asdescribed as possibly being modeled by the first model 305. As describedwith reference to FIG. 14 below, an operator specified scenario 313(e.g., one or more operator supplied commands indicating differentturbine operating points or conditions) may also be supplied to thesecond model 306 via operator input. For example, as one exemplary use,the other variables 309 may include a controller specified scenarioprovided as one or more inputs to the second model 306 when attemptingto model in real-time or near real-time current turbine behavior basedon additional inputs, such as external factors or measured inputs. Byutilizing a controller specified scenario of the first model in additionto one or more of these additional inputs, the expected real-timebehavior of the power plant 302 can be modeled by the second model 306taking into consideration these additional inputs, which may in turn beutilized to control the power plant 302 or adjust the first model 305 bycontrol profile inputs 310.

With reference to FIG. 14, an operator specified operating mode orscenario 313 is provided as one or more inputs via the interface 307 tothe second or predictive model 306, which then models or predicts futureturbine behavior under a variety of conditions. For example, an operatormay supply commands to the interface 307 to generate a scenario in whichthe power plant 302 operates at a different operating point (e.g.,different loads, configuration, efficiency, etc.). As an illustrativeexample, a set of operating conditions may be supplied via the operatorspecified scenario 313 that represent conditions that are expected forthe following day (or other future timeframe), such as ambientconditions or demand requirements. These conditions then may be used bythe second model 306 to generate expected or predicted turbine operatingcharacteristics 314 for the power plant 302 during that time frame. Uponrunning the second model 306 under the operator specified scenario, thepredicted operating characteristics 314 represent turbine behavior suchas, but not limited to, base load output capability, peak outputcapability, minimum turndown points, emissions levels, heat rate, andthe like. These modeled or predicted operating characteristics 313 maybe useful when planning and committing to power-production levels, suchas for day-ahead market planning and bidding.

FIG. 15 illustrates an example method 320 by which an embodiment of theinvention may operate. Provided is a flowchart of the basic operation ofa system for modeling a turbine, as may be executed by one or morecontrollers, such as those described with reference to FIGS. 13 and 14.The method 320 may begin at step 325, in which the controller may model,by a first or primary model, one or more current performance parametersof a turbine according to the current operation. In order to generatethis first model, the controller may receive as inputs to the model oneor more operating parameters indicating the current operation of theturbine. As described above, these operating parameters may be sensed ormeasured and/or they may be modeled, such as may occur if the parameterscannot be sensed. The current operating parameters may include anyparameter that is indicative of current turbine operation, as describedabove. It is appreciated that the methods and systems disclosed hereindo not directly depend on whether the operating parameters are measuredor modeled. The controller may include, for example, a generated modelof the gas turbine. The model may be an arrangement of one or moremathematical representations of the operating parameters. Each of theserepresentations may rely on input values to generate an estimated valueof a modeled operating parameter. The mathematical representations maygenerate a surrogate operating parameter value that may be used incircumstances where a measured parameter value is not available.

At step 330, the controller may receive or otherwise determine one ormore external factors that may impact current and/or future operation.As described above, these external factors are typically (but notrequired to be) uncontrollable, and therefore incorporating theirinfluence in the second model is beneficial to generate the desiredturbine control profile and/or operational behavior. External factorsmay include, but are not limited to, ambient temperature, humidity, orbarometric pressure, as well as fuel composition and/or supply pressure,which may impact the turbine operational behavior. These externalfactors may be measured or sensed, may be estimated or otherwiseprovided manually by an operator (such as if the operator requestspredicted behavior based on hypothetical scenarios or futureconditions), and/or may be provided by third party information sources(e.g., weather services, etc.).

At step 335, the controller may receive adjusted operating points and/orother variables to predict turbine behavior at a condition differentthan the current turbine condition. Adjusted operating points mayinclude, but are not limited, identifying the desired output level, suchas if modeling the turbine at a reserved margin (e.g., 98% of baseload), or if modeling the turbine at a peak load or during turndown, forexample. Operating points may further include operating boundaries, suchas, but not limited to, hot gas path durability (or firing temperature),exhaust frame durability, NOx emissions, CO emissions, combustor leanblow-out, combustion dynamics, compressor surge, compressor icing,compressor aero-mechanical limits, compressor clearances, and compressordischarge temperature. Thus, by providing these adjusted operatingpoints or other variables, the operator may provide hypotheticalscenarios for which the turbine model predicts the operatingcharacteristics under those scenarios, which may be useful forcontrolling future operation of the turbine and/or for planning forfuture power generation and commitments.

Following step 335 is step 340, in which a second or predictive model ofthe turbine is generated based on the first model generated at step 325and, optionally, the external factors and/or adjusted operating pointsor other variables provided at step 335. This second or predictive modelthus may accurately indicate or predict operating parameters and,therefrom, performance indicators for the turbine during a futureoperating period.

At step 345, the modeled performance may be utilized to adjust currentor future turbine operation and/or display to an operator the modeledperformance. Accordingly, if adjusting current turbine operation, theturbine controller may receive the modeled performance parameters asinputs to alter a current control model (e.g., the first model) or acurrent control profile, such as by modifying various setpoints and/orreferences utilized for current turbine control. It is anticipated thatthis real-time or near real-time control of the turbine would beperformed when the inputs to the second model generated at step 340 arerepresentative of the current turbine conditions or current externalfactors. For example, real-time or near real-time adjustment at step 345may be performed when the second model represents performancecharacteristics considering the current temperature, pressure, orhumidity, and/or considering operating parameters or performanceparameters of the turbine that more accurately represents turbinedegradation and/or efficiency. FIG. 16 describes one example embodimentthat may optionally receive operator specific inputs and generatepredicted behavior under a different operating condition. The output ofthe model generated at step 340 may also be displayed or otherwisepresented to an operator via an interface. For example, in oneembodiment in which the operator provides hypothetical operatingscenarios at step 335, the predicted turbine operating characteristicscan be displayed for analysis and possible inclusion in future controlor planning activities. Accordingly, the method 320 may end after step345, having modeled the current performance parameters of the turbine bya first model, and then modeled the same turbine in consideration ofadditional external factors, adjusted operating points, or otheradditional data so to predict turbine operation based on this additionaldata.

FIG. 16 illustrates an example method 400 by which an alternativeembodiment may operate. Provided is an example flowchart of theoperation of a system for modeling a turbine, as may be executed by oneor more controllers, such as described with reference to FIGS. 13 and14. Method 400 illustrates use of the system 301 in which an operatormay optionally supply additional variables to utilize the modelingcapabilities to predict turbine behavior under hypothetical scenarios.The method 400 may begin at decision step 405, in which it is determinedwhether the turbine is to be modeled according to current turbineoperating parameters and performance parameters, or if operator suppliedparameters are to be considered when generating the model. For example,if the system is being utilized to predict hypothetical operatingscenarios, then current performance parameters may not be needed asinputs to the model (assuming the model already reflects basic turbineoperation and behavior). Accordingly, if it is determined at decisionstep 405 that current parameters are not to be utilized, then operationsproceed to step 410 in which the operator supplies different performanceparameters, allowing for modeling the turbine under a differentoperating point and in a different operating condition (e.g., in a moredegraded state, at a different level of efficiency, etc.). Otherwise,the current performance parameters and/or operating parameters areutilized, such as is described with reference to step 325 of FIG. 15,and operations continue to step 415. At step 415, the controller maymodel, by a first or primary model, one or more performance parametersof a turbine either according to the operator supplied input from step410 or the turbine's current operation. For example, if the model isgenerated based at least in part on operator supplied parameters at step410, then the model generated at step 415 is representative of predictedturbine behavior under those performance parameters.

Following step 415 is decision step 420, in which it is determinedwhether subsequent modeling (e.g., the “second model” or the “predictivemodel”) is to be based on current external factors, such as currenttemperature, pressure, or humidity, or on different external factorssupplied by the operator. For example, in one scenario, the controllercan model turbine operating behavior based on the additional data of oneor more current external factors, which would allow further predictionof turbine behavior in light of the current conditions. In anotherscenario, however, the controller can be utilized to further model theturbine according to operator supplied conditions, which allows thepredicting of turbine operating characteristics under varioushypothetical scenarios. Accordingly, if it is determined at step 320that operator supplied external factor data is to be considered whenmodeling, then operations continue to step 425. Otherwise, operationscontinue to step 430 utilizing current external factors. At step 430 thecontroller receives external factors to be considered when generatingthe second or predictive model, whether they are representative of thecurrent state or hypothetical factors. Following step 430 are steps435-445, which optionally permit consideration of different operatingpoints, generating the predictive model based on the received data, anddisplaying the predicted behavior, respectively, in the same or similarmanner as is described with respect to steps 325-345 of FIG. 15. Themethod 400 may end after step 445, having modeled turbine operatingbehavior optionally based on operator specified scenarios,

Accordingly, embodiments described herein allow utilizing turbine modelsto indicate turbine behavior and corresponding operating parameters ofan actual turbine, in addition to predicting turbine behavior takinginto consideration the current performance parameters and one or moreexternal factors identified. These embodiments, therefore, provide atechnical effect of indicating or predicting turbine behavior atoperating points or operating conditions different than the currentturbine operation. Yet an additional technical effect is provided thatallows automated turbine control based at least in part on modeledbehavior and operating characteristics, which may optionally includecreating operator specified scenarios, inputs, operating points, and/oroperating conditions to predict turbine behavior and operatingcharacteristics at these operator specified conditions. A furthertechnical effect realized includes the ability to predict varioushypothetical scenarios allows operators to make more informed controland operating decisions, such as scheduling, loading, turn-down, etc. Aswill be appreciated, references made herein to step diagrams of systems,methods, apparatus, and computer program products according to exampleembodiments of the invention.

Referring now to FIG. 17, a flow diagram 500 is illustrated inaccordance with an alternative embodiment of the present invention. Aswill be appreciated, flow diagram 500 includes aspects that may be usedas a control method or as part of a control system for facilitating theoptimization of a power plant 501. The power plant 501 may be similar toany of those discussed in relation to FIGS. 2 and 3, though, unlessotherwise restricted in the appended claims, it should be appreciatedthat the present invention may also be used in relation to other typesof power plants. In a preferred embodiment, the power plant 501 mayinclude a plurality of thermal generating units that generateelectricity sold within a power system market, such as the one discussedin relation to FIG. 1. The power plant 501 may include many possibletypes of operating modes, which, for example, include the different waysin which thermal generating units of the plant are engage or operated,the output level of the plant, the ways in which the plant reacts tochanging ambient conditions while satisfying a load requirements, etc.It will be appreciated that the operating modes may be described anddefined by operating parameters that regard physical properties ofparticular aspects of the operation of the power plant 501. As furtherillustrated in FIG. 17, the present invention may include a power plantmodel 502. The power plant model 502 may include a computerizedrepresentation of the power plant that correlates process inputs andoutputs as part of a simulation meant to mimic operation of the plant.As shown, the present invention further includes a tuning module 503; aplant controller 505; a tuned power plant model 507; a plant operatormodule 509; and an optimizer 510, each of which will be discussedindividually below.

The power plant 501 may include sensors 511 that measure operatingparameters. These sensors 511, as well as the operating parameters thatthey measure, may include any of those already discussed herein. As partof the present method, the sensors 511 may take measurements ofoperating parameters during an initial, current, or first period ofoperation (hereinafter, “first operating period”), and thosemeasurements may be used to tune a mathematical model of the powerplant, which, as discussed below, then may be used as part of anoptimization process for controlling the power plant 501 in an improvedor optimized manner of operation during a subsequent or second period ofoperation (hereinafter “second operating period”). The measuredoperating parameters may themselves be used to evaluate plantperformance or be used in calculations to derive performance indicatorsthat relate specific aspects of the power plant's operation andperformance. As will be appreciated, performance indicators of this typemay include heat rate, efficiency, generating capacity, as well asothers. Accordingly, as an initial step, operating parameters that aremeasured by the sensors 511 during the first operating period may beused as (or used to calculate values for) one or more performanceindicators. As used herein, such values for performance indicators(i.e., those that are based on measured values of operating parameters)will be referred to herein as “measured values”. The measurements of theoperating parameters and/or the measured values for the performanceindicators, as shown, may be communicated 512 to both the plantcontroller 505 and the tuning module 503. The tuning module 503, asdiscussed in more detail below, may be configured to calculate feedbackfrom a data reconciliation or tuning process for use in tuning the powerplant model 502 so to configure the tuned power plant model 507.

The power plant model 502, as discussed, may be a computerized modelthat is configured to simulate the operation of the power plant 501.Pursuant to the present method, the power plant model 502 may beconfigured to simulate power plant operation that corresponds to thefirst operating period of the power plant 501. To achieve this, thepower plant model 502 may be supplied information and data concerningthe operating parameters of the first operating period. While thisinformation may include any of the operating parameters measured duringthe first operating period, it will be appreciated that the input datafor the power plant model 502 may be limited to a subset of theoperating parameters measured. In this manner, the power plant model 502then may be used to calculated values for selected operating parametersthat were excluded from the input data set. More specifically, the powerplant model may be supplied input data for the simulation that includesmany of the values measured for the operating parameters, but fromcertain measured values for selected operating parameter are omitted. Asan output, the simulation may be configured to predict a simulated valuefor the selected operating parameter. The present method then may usethe simulated values to predict values for the performance indicators.In this case, these values for the performance indicators will bereferred to herein as the “predicted values”. In this manner, themeasured values for the performance indicators that were determineddirectly from measured power plant operating parameters may havecorresponding predicted values. As illustrated, the predicted values forthe performance indicators may be communicated 514 to the tuning module503.

The tuning module 503 may be configured to compare the correspondingmeasured and predicted values for the performance indicators so todetermine a differential therebetween. As will be appreciated, thuslycalculated, the differential reflects an error level between actualperformance (or measurements thereof) and performance simulated by thepower plant model. The power plant model 502 may be tuned based on thisdifferential or feedback 515. In this manner, the tuned power plantmodel 507 is configured. The tuned power plant model 507, which may alsobe referred to as an offline or predictive model, then may be used todetermine optimized operating modes for a subsequent period of operationby simulating proposed or possible operating modes. The simulations mayinclude estimations or forecasts about future unknown operatingconditions, such as ambient conditions. As will be appreciated, theoptimization may be based upon one or more performance objectives 516 inwhich a cost function is defined. As illustrated, the performanceobjectives 516 may be communicated to the optimizer 510 through theplant operator module 509.

The process of tuning the plant model may be configured as a repetitiveprocess that includes several steps. As will be appreciated, accordingto certain embodiments, the power plant model 502 may include algorithmsin which logic statements and/or parameterized equations correlateprocess inputs (i.e., fuel supply, air supply, etc.) to process outputs(generated electricity, plant efficiency, etc.). The step of tuning thepower plant model 502 may include adjusting one of the algorithms in thepower plant model 502, and then simulating the operation of the powerplant 501 for the first operating period using the adjusted power plantmodel 502 so to determine the effect the adjustment had. Morespecifically, the predicted value for the performance indicator may berecalculated to determine the effect that the adjustment to the powerplant model had on the calculated differential. If the differentialturns out to be less using the adjusted power plant model 502, then thepower plant model 502 may be updated or “tuned” so to include thatadjustment going forward. It further will be appreciated that the powerplant model 502 may be constructed with multiple logic statements thatinclude performance multipliers used to reflect changes in the way thepower plant operates under certain conditions. In such cases, tuning thepower plant model 502 based on the calculated differential may includethe steps of: a) making adjustments to one or more of the performancemultipliers; b) simulating the operation of the power plant for thefirst operating period with the power plant model 502 having theadjusted performance multiplier; and c) recalculating the predictedvalue for the performance indicator using the power plant model 502 asadjusted by the performance multiplier so to determine if therecalculation results in reduced differential. These steps may berepeated until an adjustment made to one of the performance multipliersresults in reducing the differential, which would indicate that themodel is more accurately simulating actual performance. It will beappreciated that the performance multiplier, for example, may relate toexpected performance degradation based upon accumulated hours ofoperation of the plant. In another example, where the performanceindicator comprises a generating capacity, the step of tuning the powerplant model 502 may include recommending adjustments to factors based ona differential between a measured generating capacity and a predictedgenerating capacity. Such adjustments may include changes thatultimately result in the predicted generating capacity substantiallyequaling the measured generating capacity. Accordingly, the step oftuning the power plant model 502 may include modifying one or morecorrelations within the power plant model 502 until the predicted orsimulated value for a performance indicator substantially equals (or iswithin a margin of) the measured value for the performance indicator.

Once tuned, the method may then use the tuned model 507 to simulateproposed operation of the power plant. According to certain embodiments,a next step of the present method includes determining which simulatedoperation is preferable given defined performance objectives 516. Inthis manner, optimized modes of operating the power plant may bedetermined. According to a preferred embodiment, the process ofdetermining an optimized operating mode may include several steps.First, multiple proposed operating modes may be selected or chosen fromthe many possible ones. For each of the proposed operating modes,corresponding proposed parameter sets 517 may be generated for thesecond operating period. As used herein, a parameter set defines valuesfor multiple operating parameters such that, collectively, the parameterset defines or describes aspects of a particular mode of operation. Assuch, the proposed parameter sets may be configured to describe orrelate to many of the possible operating modes of the power plant 501,and may be configured as input data sets for tuned power plant model 507for simulating operation. Once the operating parameters are generatedand organized into the proposed parameter sets, the tuned power plantmodel 507 may simulate operation of the power plant 501 pursuant toeach. The optimizer 510 then may evaluate the results of the simulatedoperation 519 for each of the proposed parameter sets 517. Theevaluation may be made pursuant to the performance objectives defined bythe plant operator and the cost functions defined therein. Theoptimization process may include any of the methods described herein.

Cost functions defined by the performance objectives may be used toevaluate an economic performance of the simulated operation of the powerplant 501 over the second operating period. Based on the evaluations,one of the proposed parameter sets may be deemed as producing simulatedoperation that is preferential compared to that produced by the otherproposed parameter sets. According to the present invention, the mode ofoperation that corresponds to or is described by the proposed parameterset producing the most preferable simulated operation is designated asthe optimized operating mode. Once determined, as discussed in morebelow, the optimized operating mode may be passed along to a plantoperator for consideration or communicated to the plant controller forautomated implementation.

According to a preferred embodiment, methods of the present inventionmay be used to evaluate specific modes of operation to determine andrecommend preferable alternatives. As will be appreciated, thegenerating units of the power plant 501 are controlled by actuatorshaving variable setpoints that are controllably linked to a controlsystem, such as plant controller 505. The operating parameters of thepower plant 501 may be classified into three categories: manipulatedvariables, disturbance variables, and controlled variables. Themanipulated variables regard controllable process inputs that may bemanipulated via actuators so to control the controlled variables,whereas, the disturbance variables regard uncontrollable process inputsthat affect the controlled variables. The controlled variables are theprocess outputs that are controlled relative to defined target levels.Pursuant to preferred embodiments, the control method may includereceiving forecasted values for the disturbance variables for the secondoperating period (i.e., the period of operation for which an optimizedmode of operation is being calculated). The disturbance variables mayinclude ambient conditions, such as ambient temperature, pressure, andhumidity. In such cases, the proposed parameter sets generated for thesecond operating period may include values for the disturbance variablesthat relate to the forecasted values for the disturbance variables. Morespecifically, the generated values for each ambient condition parametermay include a range of values for each of the ambient conditionparameters. The range, for example, may include a low case, medium case,and high case. It will be appreciated that having multiple cases mayallow a plant operator to plan for best/worst case scenarios. Theforecasted values may include likelihood ratings that correspond withthe different cases, which may further assist the operator of the plantto plan for different operating contingencies and/or hedge againstlosses.

The step of generating the proposed parameter sets may includegenerating target levels for the controlled variables. The target levelsmay be generated so to correspond to competing or alternative operatingmodes of the power plant 501, and may include operator input. Suchoperator input may be prompted by the plant operator module 509.According to a preferred embodiment, such target levels may include adesired output level for the power plant 501, which may be based onlikely output levels given past usage patterns for the plant. As usedherein, “output level” reflects a load level or level of electricitygenerated by the power plant 501 for commercial distribution during thesecond operating period. The step of generating the proposed parametersets may include generating multiple cases where the output levelremains the same or constant. Such a constant output level may reflect abase load for the plant or a set of generating units. Multiple targetlevels may be generated where each corresponds to a different level ofengagement from each of the generating units and these may be drawntoward likely operating modes given historic usage. The method may thendetermine the most efficient operating mode given the known constraints.Additionally, the proposed parameter sets may be generated so that thedisturbance variables maintain a constant level for the multiple casesgenerated for each target level. The constant level for the disturbancevariables may be based upon forecasted values that were received. Insuch cases, according to one aspect of the present invention, the stepof generating the proposed parameter sets includes generating multiplecases wherein the manipulated variables are varied over ranges so todetermine an optimized operating mode for achieving a base load levelgiven the forecasted or expected ambient conditions. According toexemplary embodiments, the cost function is defined as a plantefficiency or a heat rate, or may include a more direct economicindicator, such as operating cost, revenue, or profit. In this manner,the most efficient method of controlling the power plant 501 may bedetermined in situations where a base load is known and disturbancevariables may be predicted with a relatively high level of accuracy. Theoptimized operating mode determined by the present invention in suchcases may be configured so to include a specific control solution (i.e.,specific setpoints and/or ranges therefore for the actuators thatcontrol the manipulated variables of the power plant) that might be usedby the plant controller 505 to achieve more optimal function. Calculatedin this manner, the control solution represents the optimized operatingmode for satisfying a defined or contracted target load given the valuesforecasted for the various disturbance variables. This type offunctionality may serve as an interday or inter-market periodoptimization advisor or check that analyzes ongoing operation in thebackground for the purposes of finding more efficient operating modesthat still satisfy previously fixed load levels. For example, as themarket period covered by the previous dispatch bidding progresses,ambient conditions become known or, at least, the level of confidence inprediction them accurately increases over what was estimated during thebidding process. Given this, the present method may be used to optimizedcontrol solutions for meeting the dispatched load given the more certainknowledge of the ambient conditions. This particular functionality isillustrated in FIG. 17 as the second parameter sets 517 and thesimulated operation 519 related to the second parameter sets 517. Inthis manner, the optimization process of the present invention may alsoinclude a “fine-tuning” aspect whereby simulation runs on the tunedpower plant model 507 advise on more efficient control solutions, whichmay then be communicated to and implemented by the plant controller.

Another aspect of the present invention involves its usage foroptimizing fuel purchases for the power plant 501. It will beappreciated that power plants typically make regular fuel purchases fromfuel markets that operates in a particular manner. Specifically, suchfuel markets are typically operated on a prospective basis in whichpower plants 501 predict the amount of fuel needed for a futureoperating period and then make purchases based on the prediction. Insuch systems, power plants 501 seek to maximize profits by maintaininglow fuel inventories. Power plants 501, though, regularly purchase extrafuel amounts so to avoid the costly situation of having an inadequatesupply of purchased fuel to generate the amount of power the plantcontracted to provide during the dispatch process. This of situation mayoccur when, for example, changing ambient conditions results in lessefficient power generation than predicted or the power plants truegenerating capacity is overestimated. It will be appreciated thatseveral aspects of the present application already discussed may be usedto determine an optimized mode of operation and, using that, calculate ahighly accurate prediction for the fuel supply needed. That is, thepresent optimization processes may provide a more accurate predictionregarding plant efficiency and load capabilities, which may be used toestimate the amount of fuel needed for a future operating period. Thisenables plant operators to maintain a tighter margin on fuel purchases,which benefits the economic performance of the plant.

The present invention, according to an alternative embodiment, includesa method for optimizing plant performance in which a prediction horizonis defined and used in the optimization process. As will be appreciated,a prediction horizon is a future period of operation, which is dividedinto regularly repeating intervals for the purposes of determine anoptimized mode of operation for an initial time interval of theprediction horizon. Specifically, the power plant's operation isoptimized by optimizing performance over the entire prediction horizon,which is then used to determine an optimized mode of operation for theinitial time interval. As will be appreciated, the process is thenrepeated so to determine how the power plant should be operated duringthe next time interval, which, as will be appreciated, becomes theinitial time interval relative to that next repetition of theoptimization cycle. For this subsequent optimization, the predictionhorizon may remain the same, but is redefined relative what is nowdefined as the initial time interval. This means that the predictionhorizon is effectively pushed forward into the future by an additionaltime interval each repetition. As already mentioned, a “proposedparameter set” refers to a data set that includes values for multipleoperating parameters and thereby defines or describes one of thepossible operating modes for the power plant 501. Pursuant to apreferred embodiment, the process of determining the optimized operatingmode in cases involving a prediction horizon may include one or more ofthe following steps. First, multiple proposed horizon parameter sets aregenerated for the prediction horizon. As used herein, a “proposedhorizon parameter set” includes a proposed parameter set for each of thetime intervals of the prediction horizon. For example, a 24 hourprediction horizon may be defined as including 24 1-hour time intervals,meaning that the proposed horizon parameter set includes proposedparameter sets for each of the 24 time intervals. As a next step, theproposed horizon parameter sets are used to simulate operation over theprediction horizon. Then, for each of the simulation runs, the costfunction is used to evaluate an economic performance so to determinewhich of the proposed horizon parameter sets represents the mostfavorable or, as used herein, an “optimized horizon simulation run”.According to exemplary embodiments, the operating mode described withinthe optimized horizon simulation run for the initial time interval ofthe prediction horizon may then be designated as the optimized operatingmode for the period of operation that corresponds to the initial timeinterval. The optimization process then may be repeated for subsequenttime intervals. The present invention may include receiving forecastedvalues for the disturbance variables for each of the time intervalsdefined within the prediction horizon. The proposed horizon parametersets then may be generated so that the proposed parameter set thatcorresponds to each of the time interval includes values for thedisturbance variables that relate to the forecasted values received forthe disturbance variables.

As will be appreciated, the proposed horizon parameter sets may begenerated so to cover a range of values for the disturbance variables.As before, that range may include multiple cases for each of thedisturbance variables, and may include high and low values thatrepresent, respectively, cases above and below the forecasted values. Itwill be appreciated that in accordance with any of the describedembodiments, the steps of simulating modes of operation and determiningtherefrom optimized operating modes may be repeated and configured intoa repetitive process. As used herein, each repetition is referred to asan “optimization cycle”. It will be appreciated that each repetition mayinclude defining a subsequent or next period of operation foroptimization. This subsequent period may occur just after the period ofoperation optimized by the previous cycle or may include a period ofoperation that corresponds to a future period, as may be the case, forexample, when the present method is used for the purposes of preparingdispatch bids or advising as to the economic impact of alternativemaintenance schedules.

The steps of tuning the power plant model 502 may be repeated so toupdate the tuned power plant model 507. In this manner, a tuned powerplant model 507 that reflects a recent tuning may be used withoptimization cycles so to produce more effective results. According toalternative embodiments, the optimization cycle and the cycle of tuning,the power plant model 502 may be disconnected relative to the each othersuch that each cycles according to its own schedule. In otherembodiments, the power plant model 502 may be updated or tuned after apredefined number of the repetitions of the optimization cycle. Theupdated tuned power plant model 507 then is used in subsequentoptimization cycles until the predefined number of repetitions occur soto initiate another tuning cycle. In certain embodiments, the tuningcycle occurs after each optimization cycle. According to alternativeembodiments, the number of optimization cycles that initiate a tuning ofthe power plant model 502 is related to the number of time intervals ofthe prediction horizon.

The present invention, as stated, may optimize the operation of powerplants 501 according to performance objectives, which may be defined bythe plant operator. According to preferred embodiments, the presentmethod is used to economically optimize operation of the power plant. Insuch cases, the performance objectives include and define a costfunction that provides the criteria for the economic optimization.Pursuant to exemplary embodiments, the simulated operation for each ofthe proposed parameter sets includes, as an output, predicted values forselected performance indicators. The cost function may include analgorithm correlating the predicted values for the performanceindicators to an operating cost or some other indication of economicperformance. Other performance indicators that may be used in thismanner, for example, include a power plant heat rate and/or a fuelconsumption. According to alternative embodiments, simulation outputsinclude predicted values for hot gas path temperatures for one or moreof thermal generating units of the power plant 501, which may be used tocalculate a consumed component life cost. This cost reflects a predicteddegradation cost associated with the hot gas path components thatresults from the simulated operation. The cost function may furtherinclude an algorithm correlating predicted values for the performanceindicators to an operating revenue. In such cases, the operating revenuemay then be compared to the operating cost so to reflect a net revenueor profit for the power plant 501. The present method may furtherinclude the step of receiving a forecasted price for electricity soldwithin the market for the period being optimized, and the selectedperformance indicators may include an output level of electricity, whichthen may be used to calculate expected operating revenue for theupcoming period of operation. In this manner, the present method may beused to maximize economic return by comparing operating costs andrevenue.

As will be appreciated, performance objectives may further be defined toinclude selected operability constraints. According to certainalternative embodiments, the present method includes the step ofdisqualifying any of the proposed parameter sets that produce simulatedoperation violating any one of the defined operability constraints.Operability constraints, for example, may include emission thresholds,maximum operating temperatures, maximum mechanical stress levels, etc.,as well as legal or environmental regulations, contractual terms, safetyregulations, and/or machine or component operability thresholds andlimitations.

The present method, as already mentioned, includes generating proposedparameter sets 517 that describe alternative or possible operating modesof the power plant 501. As illustrated, the proposed parameter sets 517may be generated in the plant operator module 509 and may include inputfrom a plant manager or human operators. Broadly speaking, the possibleoperating modes may be considered competing modes for which simulationis performed so to determine the mode of operation that best satisfiesperformance objectives and anticipated conditions. According toexemplary embodiments, these alternative operating modes may be selectedor defined several ways. According to a preferred embodiment, thealternative operating modes include different levels of output for thepower plant 501. Output level, as used herein, relates to the level ofelectricity generated by the power plant 501 for commercial distributionwithin the market during a defined market period. The proposed parametersets may be configured to define multiple cases at each of the differentoutput levels. Several output levels may be covered by the proposedparameter sets, and the ones chosen may be configured to coincide with arange of possible outputs for the power plant 501. It will beappreciated that the range of possible output levels may not be linear.Specifically, because of the multiple generating units of the powerplant and the scalability limitations related thereto, the proposedparameter sets may be grouped or concentrated at levels that are moreachievable or preferable given the particular configuration of the powerplant 501.

As stated, each of the competing operating modes may include multiplecases. For instances where the competing operating modes are defined atdifferent, the multiple cases may be chosen so to reflect a differentmanner by which the output level is achieved. Where the power plant hasmultiple generating units, the multiple cases at each output level maybe differentiated by how each of thermal generating units is operatedand/or engaged. According to one embodiment, the several generated casesare differentiated by varying the percentage of the output levelprovided by each of the generating units. For example, the power plant501 may include a combined-cycle power plant 501 in which thermalgenerating units include gas and steam turbines. Additionally, the erasand steam turbines may be, respectively, augmented by an inletconditioning system, such as a chiller, and a HRSG duct firing system.As will be appreciated, the inlet conditioning system, for example, maybe configured for cooling inlet air of the gas turbine so to boost itsgenerating capacity, and the HRSG duct firing system may be configuredas a secondary heat source to the boiler so to boost the generatingcapacity of the steam turbine. According to this example, the thermalgenerating units include the gas turbine or, alternatively, the gasturbine boosted by the inlet conditioning system; and the steam turbineor, alternatively, the steam turbine boosted by the HRSG duct firingsystem. The multiple cases covered by the proposed parameter sets thenmay include instances where these particular thermal generating unitsare engaged in different ways while still satisfying the differentoutput levels that were chosen as competing operating modes. Thesimulated operation may then be analyzed to determine which reflects anoptimized operating mode pursuant to a defined criteria.

According to an alternative embodiment, the proposed parameter sets maybe drawn toward different operating modes to calculate economic benefitsof maintenance operations. To achieve this, one of the competingoperating modes may be defined as one in which the maintenance operationis assumed to be completed before the period of operation chosen foroptimization. This operating mode may be defined to reflect aperformance boost that is expected to accompany the completion of thismaintenance operation. An alternative operating mode may defined asbeing one in which the maintenance operation is not performed, meaningthat the simulation of the multiple cases for this operating mode wouldnot include the expected performance boost. The results from thesimulations may then be analyzed so that the economic effects are betterunderstood, and the multiple cases may be used to show how differingscenarios (such as fluctuations in fuel prices or unexpected ambientconditions) affect the outcome. As will be appreciated, using the sameprinciples, the competing operating modes may include a turndown modeand a shutdown mode.

The present invention further includes different ways in which theoptimization process may be used by power plant operators to automateprocesses and improve efficiency and performance. According to oneembodiment, as illustrated in FIG. 17, the method includes the step ofcommunicating a calculated optimized mode of operation 521 to the plantoperator module 509 for approval by a human operator before the powerplant 501 is controlled pursuant to the optimized operating mode. In anadvisor mode, the present method may be configured to presentalternative modes of operation and the economic ramifications associatedwith each so to bring such alternatives to the attention of the plantoperator. Alternatively, the control system of the present mention mayfunction to automatically implement optimized solutions. In such cases,the optimized operating mode may be electronically communicated to theplant controller 505 so to prompt control of the power plant 501 in amanner consistent therewith. In power systems that include an economicdispatch system for distributing electricity generation among a group ofpower plants 501, the optimization method of the present invention maybe used for generating more accurate and competitive bids for submittalto the central authority or dispatcher. As one of ordinary skill in theart will appreciate, the optimization features already described may beused to generate bids that reflect true generating capacity, efficiency,heat rate, while also providing useful information to plant operatorsregarding the economic trade-offs the power plant is making in futuremarket periods by choosing between different operating modes. Increasedaccuracy of this type and the additional analysis helps ensure that thepower plant remains competitive in the bid process, while alsominimizing the risk of highly unprofitable dispatch results due tounforeseen contingencies.

FIGS. 18 through 21 illustrate exemplary embodiments of the presentinvention that relate to turndown and/or shutdown operation of a powerplant. The first embodiment, as illustrated in flow diagram 600 of FIG.18—which may be referred to as a “turndown advisor—teaches methods andsystems for simulating and optimizing a turndown level for the powerplant during a defined or selected period of operation (“selectedoperating period”). In preferred embodiments, the present method is usedwith power plants having multiple gas turbines, which may includecombined cycle plants having multiple gas turbines and one or more steamturbines. The tuned power plant model may be used to determine anoptimized minimum load for operating the power plant at a turndown levelduring the selected operating period. As previously stated, an“optimized” operating mode may be defined as one that is deemed orevaluated as preferable over one or more other possible operating modes.An operating mode for the purpose of these embodiments may include anassignment of certain power generating units to fulfill a loadcommitment or other performance objectives, as well as the physicalconfigurations of the generating units within a power plant. Suchfunctionality means that in arriving at an optimized or enhancedoperating mode, the present invention may consider a multitude of plantcombinations that take into account the different turndownconfigurations of each generating unit as well as configurations whichshutdown one or more of the units, while others remain operating at afull or turndown level. The method may further take into account otherconstraints such as operability constraints, performance objectives,cost functions, operator input, and ambient conditions in itscalculation of an enhanced turndown operating mode for the power plantthat enhances performance and/or efficiency. The present method, asdescribed herein and/or delineated in the appended claims, may take intoaccount present and predicted ambient conditions for the optimization ofthe turndown operating mode, as well as changing the unit configurationand/or control so to dynamically adjust operation of one or more of thegenerating units when actual conditions deviate from those predicted.According to a preferred embodiment, such performance is defined, atleast in part, as the one that minimizes the level of fuel usage orconsumption over the proposed turndown operating period.

The turndown advisor of the present invention may take into accountseveral factors, criteria, and/or operating parameters in arriving at anoptimized or enhanced turndown solution and/or recommended turndownaction. According to preferred embodiments, these include, but are notlimited to, the following: gas turbine engine operating boundaries(i.e., temperature, aerodynamic, fuel splits, lean blowout, mechanical,and emission limits); gas turbine and steam turbine control systems;minimum steam turbine throttle temperature; the maintenance of thevacuum seal on the condenser as well as other factors, such as theconfiguration or lineup of systems or their control. One of the outputsof the optimization may include a recommended operating mode andconfiguration of the power plant or a plurality of plants, wherein theplurality includes different types of power plants including wind,solar, reciprocating engine, nuclear, and/or other types. It will beappreciated that the recommended operating mode may be automaticallyinitiated or electronically communicated to a plant operator forapproval. Such control may be implemented via off-premise or on-premisecontrol systems that are configured to control the operation of thegenerating units. Additionally, in situations where the power plantincludes multiple gas turbine engines, the output of the present methodmay include identifying which of the gas turbines should continueoperating and which should be shutdown during the turndown period, whichis a process that is discussed in more detail in relation to FIG. 19.For each of the gas turbines that the advisor recommends for continuedoperation during the turndown period, the present method may furthercalculate a load level. Another output may include calculating the totalload for the power plant during the turndown period, as well as thehourly target load profile based on the predicted ambient conditions,which, as stated, may be adjusted if conditions change. The presentinvention may also calculate the predicted fuel consumption andemissions of the power plant during the turndown operating period. Theoutput of the disclosed method may include the operatinglineup/configuration given the control setpoints available to thegenerating units and plant so to achieve the target generating levelsmore efficiently.

As discussed above, traders and/or plant managers (hereinafter “plantoperators” unless distinguishing therebetween), who are not bound bypreexisting contractual terms, typically bid their power plants on aprospective market, such as a day ahead market. As an additionalconsideration, plant operators are tasked with making sure adequate fuelsupply is maintained so that the power plant is able to meet target orcontracted generating levels. However, in many cases fuel marketsoperate prospectively such that advantageous pricing terms are availableto power plants willing or able to commit to future fuel purchases inadvance. More specifically, the further in advance the fuel ispurchased, the more advantageous pricing. Given these market dynamics,for a power plant to achieve an optimized or high level of economicreturn, the plant operator must bid the plant competitively againstother generating units so to utilize its generating capacity, while alsoestimating accurately the fuel required for future generating periods sothat: 1) the fuel may be purchased in advance so to secure the lowerpricing; and 2) a large fuel buffer is not needed so that a lean fuelinventory may be maintained. If done successfully, the plant operatorsecures better pricing by committing early to future fuel purchases,while, at the same time, not over-purchasing so that unnecessary andcostly fuel reserves are needed, or under-purchasing so to risk a fuelsupply shortfall.

Methods of the present invention may optimize or enhance the efficiencyand profitability of power generating activities by specifying an IHRprofile for a generating unit or plant's particular configuration,especially as these relate to the preparation of a dispatch bid so tosecure generating market share. The present method may includespecifying optimal generating allocation across multiple generatingunits within a power plant or across several plants. The present methodmay take into account the operating and control configurations availableto those generating units, permutate the possible arrangements, andthereby achieve a hid that, if selected, enables the generation of powerover the bid period at a reduced or minimized cost. In doing this, thepresent method may consider all applicable physical, regulatory and/orcontractual constraints. As part of this overall process, the presentmethod may be used to optimize or enhance turndown and shutdownoperation for a power plant having multiple generating units. Thisprocedure may include taking into account anticipated exogenousconditions, such as, for example, weather or ambient conditions, gasquality, reliability of the generating units, as well as ancillaryobligations, such as steam generation. The present method may be used toenumerate IHR profiles for a plurality of generating units havingmultiple configurations, as well as control settings for the selectedturndown configuration and then control for the anticipated exogenousconditions in the preparation of the plants dispatch bid.

One common decision for operators relates to whether turndown orshutdown the power plant during off-peak periods, such as overnight,when demand or load requirements are minimal. As will be appreciated,the outcome of this decision depends significantly on the plantoperator's understanding of the economic ramifications related to eachof these possible modes of operation. In certain cases, the decision toturndown the power plant may be readily apparent, while the optimalminimum load at which to maintain the power plant during the turndownperiod remains uncertain. That is, while the plant operator has made thedecision to turndown the power plant over a certain period, the operatoris unsure about the turndown operating points at which to run theseveral generating units of the power plant in the most cost-effectivemanner.

The turndown advisor of FIG. 18 may be used as part of a process torecommend an optimal minimum load at which to operate the power plant.This advisor function may further recommend the best course of actionfor the power plant given a specific scenario of ambient conditions,economic inputs, and operating parameters and constraints. From theseinputs the process may calculate the best operating levels and then mayrecommend the operating parameters necessary for control of the powerplant, as will be discussed in more detail relative to FIG. 19. As willbe appreciated, this functionality may result in several ancillarybenefits, which include extended part life, more efficient turndownoperation, improved economic performance, and improved accuracy inmaking fuel purchases.

As illustrated in flow diagram 600, certain information and relevantcriteria may be gathered during the initial steps. At step 602, data,variables, and other factors associated with power plant systems andgenerating units may be determined. These may include any of the factorsor information listed above. According to a preferred embodiment, anambient profile may be received, which may include a forecast of ambientconditions during the selected operating period. Relevant emissions datamay also be gathered as part of this step, which may include emissionslimits as well as emissions to date for the power plant. Another factorincludes data related to the potential sale of power and/or steam duringthe selected operating period. Other variables that may be determined aspart of this step include the number of gas turbines at the plant, thecombustion and the control systems for each of the gas turbines, as wellas any other plant specific limitations that may be relevant to thecalculations discussed below.

At step 604, the period of the proposed turndown operation (or “selectedoperating period”) may be defined with particularity. As will beappreciated, this may be defined by an user or plant operation andinclude a selected operating period during which analysis of availableturndown operating modes is desired. The definition of the selectedoperating period may include it anticipated length, as well as anuser-specified start time (i.e., the time of the selected operatingperiod will start) and/or a stop time (i.e., the time the selectedoperating period will end). This step may further include defining aninterval within the selected operating period. The interval may beconfigured so to subdivide the selected operating period into aplurality of sequential and regularly spaced time periods. For the sakeof the example provided herein, the interval will be defined as a hourand the selected operating period will be defined as including aplurality of the one-hour intervals.

At step 606, the number of the gas turbines involved in the optimizationprocess for the selected operating period may be selected. This mayinclude all of the gas turbines at the power plant or some portionthereof. The method may further include the consideration of othergenerating units at the power plant, such as steam turbine systems, andtake into account their operational states during the selected operatingperiod, as described in more detail below. The determination of the gasturbines involved in the turndown operation may include prompting for orreceiving input from the plant operator.

At step 608, the present method may configure a permutation matrix giventhe number of gas turbines that were determined part of the proposedturndown operation during the selected operating period. As will beappreciated, the permutation matrix is a matrix that includes thevarious ways in which the plurality of gas turbine engines may beengaged or operated during the selected operating period. For example,as illustrated in the exemplary permutation matrix 609 of FIG. 18, thepermutation matrix for the case of two gas turbines includes fourdifferent combinations that cover each of the possible configurations.Specifically, if the power plant includes a first and a second gasturbine, the permutation matrix includes the following rows or cases: a)both the first and second gas turbines are “on”, i.e., are beingoperated in a turndown state of operation; 2) both the first and secondgas turbines are “off”, i.e., are being operated in a shutdown state ofoperation; 3) the first gas turbine is “on”, and the second gas turbineis “off”; and 4) the first gas turbine is “off”, and the second gasturbine is “on”. As will be appreciated, only two permutations arepossible in the case of a single gas turbine, while for three gasturbines, seven different rows or cases would be possible, each of whichrepresenting a different configuration as to how the three gas turbineengines may be engaged during a particular time frame in terms of the“on” and “off” operating states. In relation to FIG. 17 and theoptimization process discussed in the text related thereto, each case orrow of a permutation matrix may be thought of as representing adifferent or competing operating mode.

As part of the steps represented by steps 610, 613, 614, 616, and 618,the present method may configure proposed parameter sets for theproposed turndown operation. As stated, the selected operating periodmay be divided into the several hour-long, time intervals. The processfor configuring the proposed parameter sets may begin at step 610 whereit is determined if each of the intervals has been addressed. If theanswer to this inquiry is “yes,” then the process, as illustrated, maycontinue to an output step (i.e., step 611) wherein the output of theturndown analysis is provided to an operator 612. If all of theintervals have not been covered, the process may continue to step 613one of the intervals not already covered is selected. Then, at step 614,the ambient conditions may be set for the selected interval based uponreceived forecasts. Continuing to step 616, the process may select a rowfrom the permutation matrix, and, at step 618, set the on/off state ofthe gas turbines pursuant to the particular row.

From there, the present method may continue along two different paths.Specifically, the method may continue to an optimization steprepresented by step 620, while also continuing to a decision step atstep 621 where the process determines if all the permutations or rows ofthe permutation matrix have been covered for the selected interval. Ifthe answer to this is “no,” the process may loop back to step 616 wherea different permutation row for the interval is selected. If the answerto this is “yes,” then the process, as illustrated, may continue to step610 so to determine if all of the intervals have been covered. As willbe appreciated, once all of the rows of the permutation matrix for eachinterval have been addressed, the process may advance to the output stepof step 611.

At step 620, the present method may optimize performance using the tunedpower plant model, as previously discussed in FIG. 17. Consistent withthis approach, multiple cases may be created for each of the competingoperating modes, i.e., each of the rows of the permutation matrix foreach of the intervals of the selected operating period. According to onepreferred embodiment, the present method generates proposed parametersets in which several operating parameters are varied so to determinethe effect on a selected operating parameter or performance indicator.For example, according to this embodiment, the proposed parameter setsmay include manipulating settings for an inlet guide vanes (“IGV”)and/or an exhaust temperature of the turbine (“T_(exh)”) so to determinewhat combination yields a minimized total fuel consumption rate for thepower plant given the on/off state of the particular row and the ambientconditions forecast for the particular interval. As will be appreciated,operation that minimizes fuel consumption while satisfying the otherconstraints associated with turndown operation represents one manner bywhich turndown performance may be economically optimized or, at least,economically enhanced relative one or more alternative modes ofoperation.

As shown, according to certain embodiments, cost functions, performanceobjectives, and/or operability constraints may be used by the presentinvention during this optimization process. These may be provide via aplant operator, represented by step 622. These constraints may includelimits as to the settings of the IGV, T_(exh) limits, combustionboundaries, etc., as well as those associated with the other thermalsystems that may be part of the power plant. For example, in powerplants having combined cycle systems, the operation or maintenance ofthe steam turbine during the turndown operation may present certainconstraints, such as, for example, the maintenance of a minimum steamtemperature or condenser vacuum seal. Another operability constraint mayinclude the necessary logic that certain ancillary systems may beaffected in certain operating modes and/or certain subsystems aremutually exclusive, such as evaporative coolers and chillers.

Once the present method has cycled through the iterations given theintervals and the different rows of the permutation matrix, the resultsof the optimization may be communicated to the plant operator at step611. These results may include an optimized case for each of the rows ofthe permutation matrix for each of the time intervals. According to oneexample, the output describes an optimized operation that is defined bya cost function of fuel consumption for the power plant for each of thepermutations for each of the intervals. Specifically, the output mayinclude the minimum fuel required (as optimized using the tuned powerplant model pursuant to methods already described) for each of thepossible plant configurations (as represented by the rows of thepermutation matrix) for each interval, while also satisfying operabilityconstraints, performance objectives, and anticipated ambient conditions.According to another embodiment, the output includes an optimizationthat minimizes a generating output level (i.e., megawatts) for thepossible plant configurations for each of the intervals in the same way.As will be appreciated, certain of the possible plant configurations (asrepresented by permutations of the permutation matrix) may be unable tosatisfy operability constraints no matter the fuel supply for generatingoutput level. Such results may be discarded and not considered furtheror reported as part of the output of step 611.

FIGS. 19 and 20 graphically represent ways in which a gas turbine of apower plant may be operated over a selected operating period thatincludes defined intervals (“1” in the figures) given typicalconstraints associated with transient operation. As will be appreciated,transient operation includes switching a generating unit betweendifferent operating modes, including those involving transitioning to orfrom a shutdown mode of operation. As shown, multiple operationalpathway or sequences 639 may be achieved depending upon: 1) an initialstate 640 of the gas turbine; and 2) the decisions made regardingwhether to change operating modes at the intervals where changes arepossible given the transient operating constraints. As will beappreciated, the several different sequences 639 represent the multipleways the generating unit may be operated over the intervals shown.

As will be appreciated, the output of the method of FIG. 18 may be usedin conjunction with diagrams FIGS. 19 and 20 to configure proposedturndown operating sequences for the generating units of a power plant.That is, FIGS. 19 and 20 illustrate examples as to how a generating unitof a power plant may be engaged and how its operating modes modified asthe time intervals pass, which may include instances when the generatingunit's operating mode remains unchanged, instances when the unit'soperating mode is modified from a shutdown operating mode to a turndownoperating mode, as well as instances when the unit's operating mode ismodified from a shutdown operating mode to a turndown operating mode. Asillustrated, the transient operating constraint used in this example isthat modifying an operating modes requires that the unit remain in themodified operating mode for a minimum of at least two of the intervals.The many sequences (or pathways) by which the generating unit arrives atthe last interval represents the possible turndown operating sequencesavailable to the unit given the transient operating constraints.

As will be appreciated, the analytical results from FIG. 18—i.e., theoptimized turndown operation for each of the matrix permutations—may beused to select from the possible turndown operating sequences, aplurality of preferred cases, which may be referred to as proposedturndown operating sequences. Specifically, given the results of themethod described in relation to FIG. 18, the proposed turndown operationsequences may be chosen from cases of turndown operation that satisfyplant performance objectives and constraints, while also optimizingperformance according to a selected cost function (such as MW output orfuel consumption). The considerations illustrated in FIGS. 19 and 20represent a way of determining whether turndown operating sequences areattainable given transient operating constraints. That is, the proposedturndown operating sequences arrived at by of the combined analysis ofFIGS. 18 through 20 are operating sequences that comport with temporallimitations associated with transitioning an unit from one operatingmode to another.

Looking now at FIG. 21, a method is provided to further model andanalyze turndown operation of a power plant. As will be appreciated,this method may be used to analyze turndown costs versus shutdown costsfor specific cases involving a single generating unit over a definedtime interval. However, it may also be used to analyze plant level costsin which a recommendation is sought regarding ways in which theoperation of several generating units may be controlled over a selectedoperating period having multiple intervals. In this way, the output ofFIGS. 18 and 20 may be assembled so to configure possible operatingmodes or sequences over the span of multiple intervals, which, as willbe demonstrated, then may be analyzed pursuant to the method of FIG. 21so to provide a more fuller understanding of turndown operation over abroader operating period.

Plant operators, as already discussed, regularly have to decide betweenturndown and shutdown operating modes during off-peak hours. Whilecertain conditions may make the decision a straightforward one, oftentimes it is difficult, particularly given the increased complexity ofthe modern power plant and the multiple thermal generating units usualcontained within each. As will be appreciated, the decision to turndownversus shutdown a power plant depends significantly on a fullappreciation of the economic benefits associated with each mode ofoperation. The present invention, according to the alternativeembodiment illustrated in FIG. 21, maybe used by plant operators to gainan improved understanding of the trade-offs associated with each ofthese different operating modes so to enhance decision-making. Accordingto certain embodiments, the method of FIG. 21 may be used in tandem withthe turndown advisor of FIG. 18 so to enable a combined advisor functionthat: 1) recommends the best course of action between turndown andshutdown operating modes for the generating units of the power plantgiven known conditions and economic factors; and 2) recommends, ifturndown operation is the best course of action for some of those units,the minimum turndown load level that is optimal. In this manner, plantoperators may more readily identify situations when the units of powerplants should be turned down versus being shutdown, or vice versa, basedupon whichever represents the best economic course of action for thepower plant given a specific scenario of ambient conditions, economicinputs, and operational parameters. Ancillary benefits, such asextending component part-life, are also possible. It should also beappreciated that the methods and systems described in relation to FIGS.18 and 21 may be employed separately.

In general, the method of flow diagram 700—which also may be part of orreferred to herein as a “turndown advisor”—applies user inputs and datafrom analytical operations so to perform calculations that evaluatecosts associated with turning down a power plant versus those ofshutting it down. As will be appreciated, the flow diagram 700 of FIG.21 provides this advisor feature by, according to certain preferredembodiments, leveraging the tuned power plant model that is discussed atlength above. As part of this functionality, the present invention mayadvise as to the various outcomes, economic and otherwise, betweenturning down and shutting down a power plant during off-peak demandperiods. The present invention may provide relevant data that clarifiesas to whether turning down the power plant is preferable to shutting itdown over a specified market period. According to certain embodiments,the operation having the lower costs may be then recommended to theplant operator as the appropriate action, although, as also presentedherein, ancillary issues or other considerations may also becommunicated to the plant operator that may affect the decision. Thepresent method may put forth potential costs, as well as the probabilityof incurring such costs, and these considerations may affect theultimate decision as to which operating mode is preferable. Suchconsiderations may include, for example, a complete analysis of bothshort-term operating costs as well as long-term operating costsassociated with plant maintenance, operating efficiencies, emissionlevels, equipment upgrades, etc.

As will be appreciated, the turndown advisor may be implemented usingmany of the systems and methods described above, particularly thosediscussed in relation to FIGS. 16 through 20. The turndown advisor ofFIG. 21 may collect and use one or more of the following types of data:user specified start and stop time for the proposed turndown operatingperiod (i.e., the period for which the turndown operating mode is beinganalyzed or considered); fuel costs; ambient conditions; time offbreaker; alternate power uses; sale/price of power or steam during therelevant period; operating and maintenance cost over the period; userinput; calculated turndown load; predicted emissions for operation;current emissions levels spent by the power plant and the limits fordefined regulatory periods; specifications regarding the operation ofthe turning gear; regulation and equipment related to purge processes;fixed cost for modes of power plant operation; costs related to startupoperation; plant startup reliability; imbalance charges or penalties fordelayed startup; emissions related to startup; fuel rate used forauxiliary boiler if steam turbine present; and historical data regardinghow the gas turbines of the power plant have been operating in turndownand shutdown operating modes. In certain embodiments, as discussedbelow, the outputs from the present invention may include: a recommendedoperating mode (i.e., turndown and shutdown mode of operation) for thepower plant over the relevant period; costs associated with eachoperating mode; a recommended plant operating load and load profile overtime; a recommended time to initiate unit startup; as well as emissionsconsumed year to date and emissions remaining for the remainder of theyear. According to certain embodiments, the present invention maycalculate or predict fuel consumption and emissions of the power plantover the relevant period, which then may be used to calculate the costof turndown versus shutdown for one or more particular gas turbineengines. The present method may use the cost of each gas turbine in theshutdown and turndown mode to determine the combination which has theminimum operating cost. Such optimization may be based on differentcriteria, which may be defined by the plant operator. For example, thecriteria may be based on revenue, net revenue, emissions, efficiency,fuel consumption, etc. In addition, according to alternativeembodiments, the present method may recommend specific actions, such aswhether or not to take a purge credit; the gas turbine units that shouldbe shutdown and/or those that should be turned down (which, for example,may be based on historical startup reliability and potential imbalancecharges that may be incurred due to a delayed start). The presentinvention may further be used to enhance predictions related to fuelconsumption so to make prospective fuel purchases more accurate or,alternatively, enable fuel purchases for market periods farther into thefuture, which should have a positive effect on fuel pricing and/ormaintenance of leaner fuel inventory or margin.

FIG. 19 illustrates an exemplary embodiment of a turndown advisoraccording to an exemplary embodiment of the present invention, which isin the form of a flow diagram 700. The turndown advisor may be used toadvise as to the relative costs over a future period of operation ofshutting down a power plant or a portion thereof while operating otherof the generating units in a turndown mode. According to this exemplaryembodiment, the possible costs associated with the shutdown and theturndown operating mode may be analyzed and then communicated to a plantoperator for appropriate action.

As initial steps, certain data or operating parameters may be gatheredthat affect or may be used to determine operating costs during theselected turndown operating period. These, as illustrated, are groupedaccordingly between; turndown data 701; shutdown data 702; and commondata 703. The common data 703 includes those cost items that relate toboth shutdown and turndown operating modes. The common data 703, forexample, includes the selected operating period for which the analysisof the turndown operation mode is being performed. It will beappreciated that more than one selected operating period may be definedand analyzed separately for competing modes of turndown operation sothat a broader optimization is achieved over an extended time frame. Aswill be appreciated, the defining of the selected operating period mayinclude defining the length of the period as well as its starting or endpoint. Other common data 703, as shown, may include: the price of fuel;the various emission limits for the power plant; and data regardingambient conditions. In regard to the emission limits, the data collectedmay include limits that may be accrued during a defined regulatoryperiod, such as a year, and the amounts already accrued by the powerplant and the extent to which the applicable regulatory period hasalready tolled. Further, emissions data may include penalties or othercosts associated with exceeding any of the limits. In this manner, thepresent method may be informed as to the current status of the powerplant relative to yearly or periodic regulatory limits as well as thelikelihood of a possible violation and penalties associated with suchnoncompliance. This information may be relevant to the decision whetherto shutdown or turndown generating units as each type of operationimpacts plant emissions differently. In regard to ambient conditionsdata, such data may be obtained and used pursuant to those processesthat have been already described herein.

The turndown operating mode, as will be appreciated, has data uniquelyrelevant to a determination of the operating costs associated with it.Such turndown data 701, as illustrated, includes revenue that may beearned via the power that is generated while the power plant operates atthe turndowned level. More specifically, because the turndown operatingmode is one in which power generation continues, albeit at a lowerlevel, there is the potential that that power produces revenue for thepower plant. To the extent that this is done, the revenue may be used tooffset some of the other operating costs associated with turndownoperating mode. Accordingly, the present method includes receiving aprice or other economic indication associated with the sale orcommercial use of the power that the plant generates while operating inthe turndown mode. This may be based on historical data, and the revenueearned may depend upon the turndown level at which the power plantoperates.

The turndown data 701 may further include operating and maintenanceassociated with operating the plant at the turndown level during theselected operating period. This also may be based on historical data,and such costs may be dependent upon the turndown level for the powerplant and how the power plant is configured. In some cases, this chargemay be reflected as a hourly cost that is dependent on load level andhistorical records of similar operation. The turndown data 701 mayfurther include data related to plant emissions while operating in theturndown mode

The shutdown data 702 also includes several items that are unique to theshutdown operating mode, and this type of data may be gathered at thisstage of the current method. According to certain embodiments, one ofthese is data relating to the operation of the turning gear during theshutdown period. Additionally, data regarding the various phases ofshutdown operation will be defined. This, for example, may include datarelated to: the shutdown operation itself, which may include historicaldata on length of time necessary to bring the generating units from aregular load level to a state where the turning gear is engage; thelength of time that the power plant remains shutdown according to theselected operating period; the length of time the generating unittypically remains on the turning gear; and data regarding the process bywhich the generating units are restarted or brought back online afterbeing shutdown as well as the time required so to do this, startup fuelrequirements, and startup emissions data. In determining the startuptime, such information as to the types of startups possible for thegenerating unit and specifications related thereto may be determined. Asone of skill in the art will appreciate, startup processes may dependupon the time that the power plant remains shutdown. Anotherconsideration affecting startup time is whether the power plant includescertain features that may affect or shorten startup time and/or whetherthe operator of the power plant chooses to engage any of these features.For example, a purge process, if necessary, may lengthen the startuptime. However, a purge credit may be available if the power plant wasshutdown in a certain manner. Fixed costs associated with shutdownoperation, including those associated with startup, may be ascertainedduring this step, as well as costs particular to any of the relevantgenerating units. Emissions data associated with the startup and/orshutdown of the power plant also may be ascertained. These may be basedon historical records of operation or otherwise. Finally, data relatedto startup reliability for each of thermal generating units may beascertained. As will be appreciated, power plants may be accessed fees,penalties, and/or liquidated damages if the process of bringing unitsback online includes delays that result in the power plant being unableto meet load obligations. These costs may be determined and, asdiscussed in more detail below, may be viewed in light of the historicaldata related to startup reliability. In this manner, such charges may bediscounted so to reflect the likelihood of incurrence and/or include anexpenditure by which the risk of such charges is hedged or insuredagainst.

From the initial data acquisition steps of 701 through 703, theexemplary embodiment illustrated in FIG. 19 may proceed via a turndownanalyzer 710 and a shutdown analyzer 719, each of which may beconfigured to calculate operating costs for the operating mode to whichit corresponds. As illustrated, each of these analyzers 710, 719 mayproceed toward providing cost, emission, and/or other data to step 730where data regarding possible turndown and unit shutdown scenarios iscompiled and compared so that, ultimately, an output may be made to apower plant operator at step 731. As will be discussed, this output 731may include cost and other considerations for one or more of thepossible scenarios and, ultimately, may recommended a particular actionand the reasons therefor.

In regard to the turndown analyzer 710, the method may first determinethe load level for the proposed turndown operation during the selectedoperating period. As discussed more below, much of the costs associatedwith turndown operation may depend significantly on the load level atwhich the power plant operates as well as how the plant is configured soto generate that load, which, may include, for example, how the variousthermal generating units are engaged (i.e., which ones are turned downand which are shutdown). The turndown load level for the proposedturndown operation may be determined in several different ways accordingto alternative embodiments of the present invention. First, the plantoperator may selected the turndown load level. Second, the load levelmay be selected via analysis of historical records regarding pastturndown levels at which the plant has operated efficiently. From theserecords, a proposed load level may be analyzed and selected based onoperator supplied criteria, such as, for example, efficiency, emissions,satisfaction of one or more site specific objectives, availability ofalternative commercial uses for the power generated during the turndowncondition, ambient conditions, as well as other factors.

As a third method of selecting the turndown level for the proposedturndown operation, a computer implemented optimization program, such asthe one described in relation to FIG. 18, may be used to calculate anoptimized turndown level. In FIG. 19, this process is represented bysteps 711 and 712. An optimized turndown level may be calculated byproposing turndown operating modes at step 711 and then analyzing atstep 712 if the operational boundaries for the power plant aresatisfied. As will be appreciated, a more detailed description as to howthis is accomplished is provided above in relation to FIG. 18. By usinga process such as this to optimize the turndown level, it will beappreciated that the turndown operating modes selected for comparisonagainst the shutdown alternatives for the selected operating period willrepresent optimized case, and that, given this, the comparison betweenthe turndown and the shutdown alternatives will be a meaningful one. Asstated in relation to FIG. 18, the minimum turndown level may becalculated via an optimization process that optimizes the turndown levelpursuant to operator selected criteria and/or cost functions. One of thefunctions may be the level of fuel consumption during the proposedturndown operating period. That is, the optimized turndown level may bedetermined by optimizing fuel consumption toward a minimal level, whilealso satisfying all other operational boundaries or site specificperformance objectives.

From there, the present method of FIG. 19 may determine the costsassociated with the proposed turndown operating mode for the selectedoperating period according to the characteristics of the turndownoperating mode determined via steps 711 and 712. As illustrated, step713 may calculate fuel consumption and, therefrom, fuel costs for theproposed turndown operation. Pursuant to the exemplary embodiment justdiscussed that describes an optimization based on minimizing fuelconsumption, fuel costs may be derived by simply taking the fuel levelcalculated as part of the optimization step and then multiplying it bythe anticipated or known price for fuel. At a next step (step 715), therevenue derived from the power generated during the selected operatingperiod may be calculated given the proposed turndown level and theavailability of commercial demand during the selected operating period.Then, at step 716, operating and maintenance costs may be determined.The operating and maintenance costs associated with the proposedturndown operation may be calculated via any conventional method and maybe dependent upon the turndown level. The operating and maintenancecosts may be reflected as a hourly charge that is derived fromhistorical records of turndown operation, and may include a componentusage charge that reflects a portion of the expected life of variouscomponent system that is used during the proposed turndown operation. Ata next step, which is indicated by step 717, a net cost for the proposedturndown operating mode for the selected operating period may becalculated by adding the cost (fuel, operating and maintenance) andsubtracting the revenue.

The present method may also include step 718 that determines the plantemissions over the selected operating period given the proposed turndownoperating mode, which may be referred to as the “emissions impact”. Thenet cost and the emissions impact may then be provided to a compilationand comparison step, which is represented as step 730, so that the costand emissions impact of different turndown scenarios tray be analyzed sothat, ultimately, a recommendation may be provided at an output step731, as discussed more below.

Turning to the shutdown analyzer 719, it may be used to calculateaspects relating to operating one or more of the generating units of thepower plant at a shutdown operating mode during the selected operatingperiod. As part of this aspect of the invention, operations includingthe procedures by which the power plant is shutdown and then restartedat the end of the selected period may be analyzed for cost andemissions. According to a preferred embodiment, the shutdown analyzer719 may determine as part of initial steps 720 and 721 a proposedshutdown operating mode, which may represent an optimized shutdownoperating mode. The proposed shutdown operating mode that includesprocesses by which one or more of the generating units are shutdown andthen restarted so to bring the units back online at the end of theselected operating period. As will be appreciated, the length of thetime period during which a generating unit is not operating willdetermine the type of possible startup processes available to it. Forexample, whether a hot or cold startup is available depends,respectively, on if the shutdown period is a brief or long one. Indetermining the proposed shutdown operating mode, the present method maycalculate the time necessary for the startup process to bring thegenerating unit back to an operational load level. At step 721, themethod of the present invention may check to make sure that the proposedshutdown operating procedure satisfies all operating boundaries of thepower plant. If one of the operational boundaries is not satisfied, themethod may return to step 720 so to calculate an alternative startupprocedure. This may be repeated until an optimized startup procedure iscalculated that satisfies the operational boundaries of the power plant.As will be appreciated, pursuant to the methods and systems discussedabove, the tuned power plant model may be used to simulated alternativeshutdown operating modes so to determine optimized cases given therelevant operating period and project ambient conditions.

Given the proposed shutdown operating mode of steps 720 and 721, theprocess may continue by determining the costs associated with it.Initial steps include analyzing the nature of the startup process thatthe shutdown operating mode includes. At step 722, the process maydetermine the specific operating parameters of the startup, which mayinclude a determination as to whether or not a purge is required orrequested by a plant operator. Given the determined startup, fuel costsmay be determined at step 723. According to an exemplary embodiment, theshutdown analyzer 719 then calculates costs associated with the delaysthat are sometimes incurred during the startup process. Specifically, asindicated in step 724, the process may calculate the probability of sucha delay. This calculation may include as inputs the type of startup aswell as historical records regarding past startups of the relevantgenerating units at the power plant as well as data regarding startupsof such generating units at other power plants. As part of this, theprocess may calculate a cost related to the proposed shutdown operatingmode that reflects the probability of a start delay occurring and thepenalties, such as liquidated damages, that would be incurred. This costmay include any cost associated with a hedging tactic by which the powerplant passes a portion of the risk of incurring such penalties to aservice provider or other insurer.

At step 726, the current method may determine costs associated withoperating the turning gear during the shutdown process. The method maycalculate a speed profile for the turning gear given the shutdown periodand, using this, a cost for the auxiliary power needed to operate theturning gear is determined. As will be appreciated, this represents thepower required to keep the rotor blades of the gas turbine turning asthey cool, which is done to prevent the warping or deformation thatotherwise would occur if the blades were allowed to cool in a stationaryposition. At step 727, as illustrated, operating and maintenance costsfor the shutdown operation may be determined. The operating andmaintenance costs associated with the proposed shutdown may becalculated via any conventional method. The operating maintenance costsmay include a component usage charge that reflects a portion of theexpected life of various component system that is used during theproposed shutdown operation. At a next step, which is indicated by step728, a net cost for the proposed shutdown operating mode for theselected operating period may be calculated by adding the determinedcosts of fuel, turning gear, and operating and maintenance. The presentmethod may also include step 729 in which plant emissions are determinedover the selected operating period given the proposed shutdown operatingmode, which, as before, may be referred to as the “emissions impact” ofthe operating mode. The net cost and the emissions impact may then beprovided to the compilation and comparison step of step 730.

At step 730, the current method may compile and compare various plantturndown operating modes for the selected operating period. According toone embodiment, the current method may analyze competing turndownoperating modes that were identified as part of the methods andprocesses described in relation to FIGS. 18 through 20. At step 730, thecompiled cost data and emissions impact for each of the competingturndown operating modes may be compared and provided as an output aspart of step 731. In this manner, according to how the competingoperating modes compare, a recommendation may be provided as to how thepower plant should be operated during the selected turndown operatingperiod, including which of the turbines should be shutdown and which ofthe turbines should be turned down and the turndown level at which theyshould be operated.

Emissions data may also be provided as part of the output of step 731,particular in instances where the competing modes of operation analyzedhave similar economic results. As will be appreciated, notification asto how each alternative impacts plant emissions and, given the impact,the likelihood of noncompliance during the present regulatory period mayalso be provided, as well as an economic result related thereto.Specifically, the accumulated emissions of one or more power plantpollutants during the regulatory period may be compared to the overalllimits allowable during that timeframe. According to certain preferredembodiments, the step of communicating the result of the comparison mayinclude indicating an emission rate of the power plant derived byaveraging a cumulative emission level for the power plant over a portionof a current regulatory emission period relative to an emission ratederived by averaging a cumulative emission limit over the currentregulatory emission period. This may be done to determine how the powerplant stands when compared to the average emissions rate allowablewithout incurring a violation. The method may determine the emissionsstill available to the power plant during the current regulatory period,and whether or not there is sufficient levels available to accommodateeither of the proposed operating modes or, rather, if the emissionsimpact impermissibly increases the probability of a future regulatoryviolation.

As an output, the present method may provide a recommended action whichadvises as to the advantages/disadvantages, both economic and otherwise,between the proposed turndown and shutdown modes of operation. Therecommendation may include a reporting of costs as well as a detailedbreakdown between the categories in which those costs were incurred andthe assumptions made in calculating them. Additionally, the recommendedaction may include a summary of any other considerations which mightaffect the decision whereby the most favorable operating mode isselected. These may include information related to applicable emissionlimits and regulatory periods, as well as where the power plant'scurrent cumulative emissions stand in relation thereto. This may includepower plant operators being notified as to any operating mode thatunreasonably increases the risk of violating emission thresholds as wellas the cost related to such violations.

The present invention may further include an unified system architectureor integrated computing control system that efficiently enables andimproves performance of many of the functional aspects described above.Power plants—even those commonly owned—often operate across differentmarkets, governmental jurisdictions, and time zones, include many typesof stakeholders and decision-makers participating in their management,and exist under varying types of servicing and other contractualarrangements. Within such varied settings, a single owner may controland operate a number of power plants, each of which having multiplegenerating units and types, across overlapping markets. Owners also mayhave different criteria for evaluating effective power plant operation,which, for example, may include unique costs models, response time,availability, flexibility, cyber security, functionality, anddifferences inherent in the ways separate markets operate. However, aswill be appreciated, most current power trading markets rely on variousoff-line generated files shared by multiple parties and decision-makers,including those transmitted between traders, plant managers, andregulating authorities. Given such complexities, the capabilities ofpower plants and/or generating unit within a market segment may not befully understood, particularly across the layered hierarchy that spans,for example, from individual generating units to power plants, or frompower plants to fleets of such plants. As such, each successive level ofthe power trading market typically hedges the performance that isreported by the level below. This translates into inefficiencies andlost revenue for owners, as the successive hedging compounds intosystemic underutilization. Another aspect of the present invention, asdiscussed below, functions to alleviate the disconnections that are atthe root of these issues. According to one embodiment, a system orplatform is developed which may perform analytics, collect and evaluatehistorical data, and perform what-if or alternate scenario analyses onan unified system architecture. The unified architecture may moreefficiently enable various functions, various components, such as powerplant modeling, operational decision support tools, prediction of powerplant operation and performance, and optimization pursuant toperformance objectives. According to certain aspects, the unifiedarchitecture may achieve this via an integration of components local tothe power plant with those remote to it, such as, for example, thosehosted on a centrally hosted or cloud based infrastructure. As will beappreciated, aspects of such integration may enable enhanced and moreaccurate power plant models, while not impacting consistency, efficacy,or timeliness of results. This may include utilizing the alreadydiscussed tuned power plant models on local and externally hostedcomputing systems. Given its deployment on an externally hostedinfrastructure, the system architecture may be conveniently scale tohandle additional sites and units.

Turning now to FIGS. 22 through 25, scalable architecture and controlsystems are presented which may be used to support the many requirementsassociated with controlling, managing, and optimizing a fleet of powerplants in which multiple generating units are dispersed across severallocations. A local/remote hybrid architecture, as provided herein, maybe employed based on certain criteria or parameters that are situationalor case specific. For example, an owner or operator having a series ofpower plants may desire that certain aspects of the systemsfunctionality be hosted locally, while others are centrally hostedenvironment, such as in a cloud based infrastructure, so to pool datafrom all of the generating units and act as a common data repository,which may be used to scrubbed the data via cross-referencing values fromcommon equipment, configurations, and conditions, while also supportinganalytic functions as well. The method of choosing the suitablearchitecture for each of the various types of owner/operators may focuson the significant concerns that drive the operation of the powerplants, as well as the specific characteristics of the power market inwhich the plants operate. According to certain embodiments, as providedbelow, performance calculations may be performed locally so to supportthe closed loop control of a particular power plant, improve cybersecurity, or provide the response speed needed to accommodate nearreal-time processing. On the other hand, the present system may beconfigured such that data flow between local and remote systems includeslocal data and model tuning parameters that are transferred to thecentrally hosted infrastructure for the creation of a tuned power plantmodel that is then used for analytics, such as alternative scenarioanalysis. Remote or centrally hosted infrastructure may be used totailor interactions with a common plant model according to the uniqueneeds of the different user types that require access to it.Additionally, a strategy for scaling may be determined based on responsetime and service agreements that depend on the unique aspects of aparticular market. If faster response times are required on theavailability of final results, then the analytic processes may be scaledboth in terms of software and hardware resources. The systemarchitecture further supports redundancy. If any system runninganalytics becomes inoperable, the processing may be continued on aredundant node that includes the same power plant models and historicaldata. The unified architecture may bring applications and processestogether so to promote performance and increase the scope offunctionality so to achieve both technical and commercial advantages. Aswill be appreciated, such advantages include: convenient integration ofnew power plant models; separation of procedures and models; theenablement of different operators to share the same data in real-timewhile also presenting the data in unique ways pursuant to the needs ofeach of the operators; convenient upgrades; and compliance with NERC-CIPlimitations for sending supervisory controls.

FIG. 22 illustrates a high-level logic flow diagram or method for fleetlevel optimization according to certain aspects of the presentinvention. As shown, the fleet may include multiple generating units orassets 802, which may represent separate generating units acrossmultiple power plants or the power plants themselves. The assets 802 ofthe fleet may be owned by a single owner or entity, and compete againstother such assets across one or more markets for contract rights togenerate shares of the load required by a customer grid. The assets 802may include multiple generating units that have the same type ofconfigurations. At step 803, performance data that is collected by thesensors at the various assets of the plants may be communicatedelectronically to a central data repository. Then, at step 804, themeasured data may be reconciled or filtered so, as described below, amore accurate or truer indication of the performance level for eachasset is determined.

As described in detail above, one way in which this reconciliation maybe done is to compare the measured data against corresponding datapredicted by power plant models, which, as discussed, may be configuredto simulate the operation of one of the assets. Such models, which alsomay be referred to as off-line or predictive models, may include physicsbased models and the reconciliation process may be used so toperiodically tune the models so to maintain and/or improve the accuracyby which the models represent, via simulation, actual operation. Thatis, as previously discussed in detail, the method, at step 805, may usethe most currently collected data to tune the power plant models. Thisprocess may include tuning the models for each of the assets, i.e., eachof the generating units and/or power plants, as well as more generalizedmodels covering the operation of multiple power plants or aspects offleet operation. The reconciliation process also may involve thecollected data being compared between similar assets 802 so to resolvediscrepancies and/or identify anomalies, particularly data collectedfrom the same type of assets having similar configurations. During thisprocess, gross errors may be eliminated given the collective andredundant nature of the compiled data. For example, deference may begiven to sensors having higher accuracy capabilities or those that areknown to have been checked more recently and demonstrated to beoperating correctly. In this manner, the data collected may becomparatively cross-checked, verified and reconciled so to construct asingle consistent set of data that may be used to calculate moreaccurate actual fleet performance. This set of data may then be used totune off-line assets models that may then be used to simulate anddetermine optimized control solutions for the fleet during a futuremarket period, which, for example, may be used to enhance thecompetitiveness of the power plant during dispatch bidding procedures.

At step 806, as illustrated, the true performance capabilities of thepower plant are determined from the reconciled performance data and thetuned models of step 805. Then, at step 807, the assets 802 of the fleetmay be collectively optimized given a selected optimization criteria. Aswill be appreciated, this may involve the same processes alreadydiscussed in detail above. At step 808, an optimized supply curve orasset schedule or may be produced. This may describe the manner in whichthe assets are scheduled or operated as well as the level at which eachis engaged so to, for example, satisfy a proposed or hypothetical loadlevel for the power plant fleet. The criteria for optimization may bechosen by the operator or owner of the assets. For example, theoptimization criteria may include efficiency, revenue, profitability, orsome other measure.

As illustrated, subsequent steps may include communicating the optimizedasset schedule as part of a bid for load generating contracts for futuremarket periods. This may include, at step 809, communicating theoptimized asset schedule to energy traders who then submit a bidaccording to the optimized asset schedule. As will be appreciated, atstep 810, the bids may be used to take part in a power system widedispatch process by which load is distributed among multiple powerplants and generating units located within the system, many of which maybe owned by competing owners. The bids or offers for the dispatchprocess may be configured pursuant to a defined criteria, such asvariable generating cost or efficiency, as determined by the particulardispatcher of the power system. At step 811, the results of theoptimization of the power system may be used to generate an assetschedule that reflects how the various assets in the power system shouldbe engaged so to meet predicted demand. The asset schedule of step 811,which reflects the outcome of the system-wide optimization ordispatching process, may then be communicated back to the owners of theassets 802 so that, at step 812, operating setpoints (or particularlyoperating modes), which may include, for example, the load at which eachof the assets is operated, may be communicated to a controller thatcontrols the operation of the assets 802. At step 813, the controllermay calculate and then communicate a control solution and/or directlycontrol the assets 802 so to satisfy the load requirements that itcontracted for during the dispatch process. Fleet owners may adjust theway one or more power plants operate as conditions change so to optimizeprofitability.

FIG. 23 illustrates the data flow between local and remote systemsaccording to an alternative embodiment. As stated, certain functionalitymay be locally hosted, while other functionality is hosted off-site in acentrally hosted environment. The method of choosing the suitablearchitecture according to the present invention includes determining theconsiderations that are significant drivers of the operation of theassets within the fleet. Accordingly, considerations such as cybersecurity concerns might require certain systems remain local.Time-consuming performance calculations also remain locally hosted sothat necessary timeliness is maintained. As illustrated in FIG. 23, alocal plant control system 816 may take in sensor measurements andcommunicate the data to a tuning module 817 where, as discussedpreviously, particularly in relation to FIG. 17, a tuning or datareconciliation process may be completed using performance calculationsthat compare actual or measured values against those predicted by theplant or asset model. Via data router 818, as illustrated, the modeltuning parameters and reconciled data then may be communicated to acentrally hosted infrastructure, such as remote central database 819.From there the model tuning parameters are used to tune the off-linepower plant model 820, which then may be used, as described above, tooptimize future fleet operation, provide alternate scenario or “what-if”analysis, as well as advise between possible or competing modes ofoperating the asset fleet.

The results of the analytics performed using the off-line power plantmodel 820, as illustrated, may be communicated to fleet operators via aweb portal 821. The web portal 821 may provide customized access 822 tousers for the management of the fleet. Such users may include plantoperators, energy traders, owners, fleet operators, engineers, as wellas other stakeholders. Pursuant to the user interaction through theweb-portal access, decisions may be made regarding the recommendationsoffered by the analytics performed using the off-line power plant model820.

FIGS. 24 and 25 illustrate a schematic system configurations of anunified architecture according to certain alternative aspects of thepresent invention. As illustrated in FIG. 25, a remote centralrepository and analytics component 825 may receive performance andmeasured operating parameters from several assets 802 so to perform afleet level optimization. The fleet level optimization may be based onadditional input data, which, for example, may include: the current fuelamounts stored and available at each power plant, the location specificprice for fuel for each power plant, the location specific price forelectricity generated at each power plant, current weather forecasts andthe dissimilarities between remotely located assets, and/or outage andmaintenance schedules. For example, a scheduled component overhaul for agas turbine may mean that short-term operation at higher temperatures ismore economical. The process may then calculate a supply curve, whichincludes an optimized variable generating cost for the fleet of powerplants. Additionally, the present invention, as illustrated, may enablemore automated bid preparation so that, at least in certaincircumstances, the bid may be transferred directly to the system widedispatch authority 826, and thereby bypass energy traders 809. Asillustrated in FIG. 25, the results of the optimization of the powersystem (via the system wide dispatch authority) may be used to producean asset schedule that reflects how the various assets in the powersystem should be engage so to meet predicted demand. This asset schedulemay reflect a system-wide optimization, and, as illustrated, may becommunicated back to the owners of the fleet of assets 802 so thatoperating setpoints and operating modes for the assets may becommunicated to the controller that controls each asset in the system.

Accordingly, methods and systems may be developed pursuant to FIGS. 22through 25 by which a fleet of power plants operating within acompetitive power system is optimized toward enhanced performance andbidding related to future market periods. Current data regardingoperating conditions and parameters may be received in real-time fromeach of the power plants within the fleet. The power plant and/or fleetmodels may then be tuned pursuant to the current data so that the modelsaccuracy and range of prediction continue to improve. As will beappreciated, this may be achieved via the comparison between measuredperformance indicators and corresponding values predicted by power plantor fleet models. As a next step, the tuned power plant models and/orfleet level models may be used to calculate true generating capabilitiesfor each of the power plants within the fleet based upon competingoperating modes that are simulated with the tuned models. Anoptimization then is performed using the true plant capabilities andoptimization criteria defined by the plant or fleet operator. Upondetermining an optimized mode of operation, an asset schedule may beproduced that calculates optimal operating points for each of the powerplants within the fleet. As will be appreciated, the operating pointsmay be then transferred to the different power plants for controllingeach consistent therewith, or, alternatively, the operating points mayserve as the basis on which bids for submission to the central dispatchauthority are made.

Also related to centralize control and optimization of multiple powerunits, FIGS. 26 and 27 illustrates a power system 850 in which a blockcontroller 855 is used to control a plurality of power blocks 860. Thepower blocks 860, as indicated, may define a fleet 861 of the generatingassets (“assets”). As will be appreciated, these embodiments provideanother exemplary application of the optimization and control methodsdescribed in more detail above, though include broadening theoptimization perspective to a fleet level. In so doing, the presentinvention may further offer ways of reducing certain inefficiencies thatstill impact modern power generating systems, particularly those havinga large number of remote and varied thermal generating units. Each ofthe assets may represent any of the thermal generating units discussedherein, such as, for example, gas and steam turbines, as well as relatedsubcomponents, like HRSGs, inlet conditioners, duct burners, etc. Theassets may be operable pursuant to multiple generating configurationsaccording to how the subcomponents are engaged. The power generationfrom the multiple power blocks 860 may be centrally controlled by ablock controller 855. With respect to the system in FIG. 27, which willbe discussed in more detail below, the block controller 855 may controlthe system pursuant to optimization processes that take intoconsideration asset and power block health, as well as generationschedules, maintenance schedules, as well as other factors that might beparticular to one of the assets or power blocks 860, including locationdependent variables. In addition, learning from operational datacollected from similarly configured assets and power blocks, but notpart of the fleet, may be utilized so to further refine controlstrategies.

Typically, conventional asset controllers (which are indicated in FIG.26 as “DCS”) are local to the generating assets and operate insubstantial isolation. Because of this, such controllers fail to takeinto account the current health of the other assets that make up thepower block 860 and/or fleet 861. As will be appreciated, this lackperspective leads to less than optimal power generation for the fleet861 when considered from that perspective. With continued reference tothe methods and systems already described, particularly those pertainingto FIGS. 3, 4, and 17 through 25, the present exemplary embodimentteaches a fleet level control system that enables several system-widebenefits, including enhanced power sharing strategies,cost-effectiveness, and improved efficiencies across grouped assets orpower blocks.

As indicated, the control system, as represented by the block controller855, may interact with the asset controllers. The block controller 855also may communicate with the grid 862, as well as with a centraldispatch or other governing authority that is associated with itsmanagement. In this manner, for example, supply and demand informationmay be exchanged between the fleet 861 and a central authority.According to an exemplary embodiment, supply information, such asdispatch bids, may be based on the block controller's optimization ofthe fleet 861. The present invention may further include optimizationprocesses that occur between bid periods, which may be used periodicallyto optimize the way in which the fleet 861 is configured so to satisfyan already established load level. Specifically, such inter-bidoptimization may be used to address dynamic and unanticipated operatingvariables. Appropriate control actions for the assets of the powerblocks 860 may be communicated by the block controller 855 to thecontrol systems within each of the power blocks 860 or, more directly,to the assets. According to preferred embodiments, implementation ofcontrol solutions of the block controller 855 may include enabling it tooverride asset controllers when certain predefined conditions are met.Factors affecting such override may include variable generating cost foreach of the power blocks/assets, remaining useful part-life of hot gaspath components, changing levels of demand, changing ambient conditions,as well as others.

The block controller 855, as illustrated, may be communicatively linkedto the several power blocks 860 of the fleet 861 as well as directly tothe assets, and thereby may receive many data inputs upon which thecontrol solutions described herein are based. The optimizationprocedures may consider one or more of the following inputs: health andperformance degradation; power generation schedules; grid frequency;maintenance and inspection schedules; fuel availability; fuel costs;fuel usage patterns and predictions; past issues and equipment failures;true performance capabilities; lifing models; startup and shutdownfeatures; measurement operating parameter data, past and present;weather data; cost data; etc. As discussed in more detail in relation toother embodiments, inputs may include detailed present and historicaldata regarding measured operating parameters for each of the generatingassets of the fleet 861. All such inputs, past and present, may bestored pursuant to conventional methods in, for example, a centraldatabase, and thereby made available upon query from the blockcontroller 855 as might be necessary according to any of the proceduralsteps described herein.

A cost function may be developed according to the preferences of a fleetoperator. According to a preferred embodiment, a weighted average sum ofa fleet robustness index may be used to determine preferable oroptimized power sharing configurations. The fleet robustness index mayinclude, for example, an optimization according to several factors thatis applicable to a given demand or fleet output level. These factors mayinclude: thermal and mechanical stresses; degradation or losses,including rate of degradation; cost of generation; and/or fuelconsumption. In this manner, the present embodiment may be used toaddress several ongoing issues relating to fleet control, particularly,optimizing performance across several power blocks having multiple andvaried generating assets.

Data inputs may include the types already discussed herein, includingthose related to computer modeling, maintenance, optimization, andmodel-free adaptive learning processes. For example, according to thepresent embodiment, computer models, transfer functions, or algorithmsmay be developed and maintained so that the operation (or particularaspects of the operation) of the assets and/or, collectively, the powerblocks or the fleet, may be simulated under a variety of scenarios.Results from the simulations may include values for certain performanceindicators, which represent predictions as to aspects of the operationand performance of the assets, power block, or fleet performance overthe selected operating period. The performance indicators may beselected because of a known or developed correlation to one or more costresults, and thus may be used to compare the economic aspects of eachsimulation. A “cost result”, as used herein, may include any economicramification, positive or negative, associated with the operation of thefleet 861 over the selected operating period. Cost results, thus, mayinclude any revenue earned from the generation of power over the period,as well as any operating and maintenance costs incurred by the fleet.These operating and maintenance costs may include resulting degradationto the assets of the fleet given the scenarios and the simulatedoperation resulting from each. As will be appreciated, data extractedfrom the simulation results may be used to calculate which of thealternative operating modes for the fleet is/are more desirable orcost-effective.

The models for the assets, blocks or fleet may include algorithms ortransfer functions developed through physics-based models, adaptive orlearned “model free” process input/output correlations, or combinationsthereof. Baseline degradation or loss models may be developed thatcorrelate process inputs/outputs to degradation or loss data for eachasset type. The degradation or loss data and the cost result relatedthereto, thus, may be calculable based on the predicted values for theoperating parameters of proposed, alternative or competing operatingmodes of the fleet, which, according to certain embodiments, may bedifferentiated by the manner in which the assets and power blocks areengaged, the way in which generation is shared across the fleet assets,as well as other factors described herein. As stated, learning fromsimilarly configured assets may be used to inform or further refine themodels used as part of this process. For example, degradation model maybe developed that calculate accrued equipment degradation and lossesgiven the values for selected performance indicators. Such degradationthen may be used to calculate the economic ramifications or cost resultfor each of the competing operating modes. Those economic ramificationsmay include degradation to asset performance, wear to components,expended useful part-life (i.e., the portion of the useful life of acomponent that is expended during a period of operation), as well asother measures of value, such as, for example, costs related toemissions, regulatory fees, fuel consumption, as well as other variablecosts that are dependent upon output level. As will be appreciated,because the degradation and the expenditure of useful part-life for aparticular asset may accrue in a nonlinear fashion as well as beingdependent on dynamic and/or location specific variables, significantcost savings may be achieved over time by distributing the output levelof the fleet so to minimize overall fleet degradation, particularly ifthat minimization is shared across the assets so to minimally impactoverall fleet generating capacity and efficiency.

Thus, taking into account conditions predicted for a future marketperiod, which may include anticipated demand and ambient conditionsforecasts, a plurality of competing operating modes for the fleet may beselected for analysis and/or simulation so to determine an optimized,or, at least, preferred fleet operating mode. Each of the competingfleet operating modes may describe an unique generating configurationfor the fleet 861. The competing fleet operating modes may be developedso to include parameter sets and/or control settings that define theunique generating configurations by which a particular fleet outputlevel is reached. As mentioned, the fleet output level may be selectedin a number of ways. First, it may be selected to reflect an alreadyknown fleet output level, for example, an output level established via arecently concluded dispatch process such that the optimization processmay be used to determine an optimized fleet configuration by which thatparticular output level is satisfied. The fleet output level also may beselected pursuant to an expected load level given historical generationrecords, expected customer demand and/or other forecasted conditions.Alternatively, the fleet output level may also be varied over a chosenrange. In this way a variable generating cost for the fleet 861 may becalculated and then, for example, used as part of a bidding procedure soto inform the preparation of a competitive bid. Thus, the manner inwhich the fleet output level is defined by the fleet operator may beused so that, in one instance, activities around preparing a competitivebid is supported, while, at other times, the output level may beselected so to support an advisor function that operates to optimizefleet performance as actual conditions might stray from thoseanticipated.

According to exemplary operation, as indicated by the more detailedsystem of FIG. 27, parameter sets may be developed that describe each ofthe competing fleet operating modes, and, for each of the competingfleet operating modes, different scenarios or cases may be developedwithin which manipulable variables are varied over a selected range soto determine the effect of the variation on the overall operation of thefleet. The different cases for the competing fleet operating modes maybe configured so to cover alternative ways in which the fleet outputlevel is shared across the power blocks 860 and/or assets. According toanother example, the different cases may be selected based onalternative configurations available to certain of the assets, includingthe various ways by which each of the assets is engaged. For example,some cases may include the engagement of certain subcomponents of theassets, such as duct burners or inlet conditioners, so to augment powergeneration capabilities, while recommending that other assets operate atshutdown or turndown levels. Other scenarios may explore situations inwhich those asset configurations are varied somewhat or altogetherreversed.

As illustrated in FIG. 27, the block controller 855 may communicate witha data and analytics component 865, which may include several modules bywhich relevant data is collected, normalized, stored, and made availableupon query to the block controller 855. A data records module mayreceiving real-time and historical data inputs from a monitoring systemassociated with generating assets. A module related to performancemonitoring may also be included, and related thereto one or moreoff-line models may be maintained. Each of these modules may functionsubstantially consistent with other embodiments discussed herein. Alearning module may also be included for the collection of operatingdata from similarly configured assets or power blocks that are notoperating within the fleet 861. This data, as will be appreciated, maysupport a learning function by which a deeper and more thoroughoperational understanding of the assets is obtained. Such data may alsobe used to normalize measured data collected from the fleet 861 so thatperformance degradation of the generating assets may be calculatedaccurately, which may include accounting for the effects of othervariables, such as fuel characteristics, ambient conditions, etc., thatalso may affect output capacity and efficiency.

As described in relation to FIGS. 24 and 25, fleet level optimizationmay be based on locality-dependent variables. These variables mayreflect conditions that are unique and apply to certain particularassets or power blocks, and, for example, may include: the current fuelamounts stored and available at each asset; the location specific pricefor fuel for each asset; the location specific market price forelectricity generated at each asset; current weather forecasts and thedissimilarities between remotely located assets within the fleet; andoutage and maintenance schedules for each asset. For example, ascheduled component overhaul for a gas turbine asset may mean thatshort-term operation at higher temperatures is more economicallybeneficial. As illustrated, the data and analytics component 865 mayinclude a module for accounting for these differences.

The block controller 855, as indicated, further may include modulesdirected toward power generation models (which may include asset models,block models, fleet models, as well as degradation or loss models), anoptimizer, and a cost function. The asset, power block, and/or fleetmodels may be created, tuned and/or reconciled and maintained accordingto the methods already described herein. These models may be used tosimulate or otherwise predict the operation of the fleet, or a selectedportion thereof, over the selected operating period such that theoptimizer module is able to determine a preferred scenario according toa defined cost function. More specifically, the results from thesimulations may be used to calculate a cost result for each, which mayinclude a summation across the power blocks and/or fleet assets ofrevenue, operating costs, degradation, expended useful part-life, andother costs mentioned herein. The revenue, as will be appreciated, maybe determined via a projected output level multiplied by a market unitprice. The calculation of the costs, as stated, may include degradationmodels or algorithms that correlate an economic result to the manner inwhich the assets operate within the simulations. Performance data fromthe simulation results may be used to determine fleet-wide operatingcosts, degradation, and other losses as already described. As will beappreciated, certain cost considerations, such as fixed aspects ofoperating costs, may not be appreciable different between the competingfleet operating modes and, thus, be excluded from such calculations.Additionally, the simulations described herein may be configured so toinclude the entire fleet of assets or a portion thereof, and may befocused on limited aspects of asset operation that, as provided herein,have been found particularly relevant at predicting cost results.

According to certain embodiments, the cost function module may include afleet robustness index so to efficiently differentiate betweenalternative operating modes. The fleet robustness index may represent anaveraged summation of losses accrued within the power blocks. Therobustness index may include a factor indicating costs related toexpended useful part-life, which may be a summation of the part-lifeexpended across the assets, such as hot gas path parts and compressorblades in gas turbines. For example, a generating asset that isscheduled to be shutdown during the selected operating period pursuantto one of the competing fleet operating modes will incur an economicloss corresponding to the useful part-life expended per eachshutdown/startup procedure. Whereas, a generating asset scheduled tooperate at full load during the same operating period may incur a losscommensurate to those hours of operation. As will be appreciated, suchlosses may be further calibrated to reflect specific the thermal andmechanical loads that are expected given the load level and theoperating parameters predicted to satisfy a particular load level,which, for example, may depend upon such factors as forecasted ambientconditions, fuel characteristics, etc. Other economic losses may beincluded within the summation of fleet losses so to derive a cost resultfor each of the competing fleet operating modes. These may include asummation of fuel consumption for the fleet assets, as well as, forexample, the economic impact of predicted emission levels given thesimulation results.

Once the summation of fleet-wide revenue and/or losses is complete foreach of the simulated scenarios, the present method may include the stepof calculating one or more preferred or optimized cases. The presentmethod then may include one or more outputs that relate to the preferredor optimized cases. For example, the preferred or optimized cases may beelectronically communicated to a fleet operator, such as through userinterface 866. In such cases, outputs of the present method may include:a power block block/asset health advisor; a power sharingrecommendation; an outage planner; an optimal setpoints control solutionfor the power blocks; DCS override; and/or an expected generationschedule. The output also may include an automated control response,which may include automatically overriding one of the asset controllers.According to another alternative, an output may include generating adispatch bid according to one or more of the preferred or optimizedcases. As will be appreciated, the outputs of the method, as indicatedon the user interface 866, may enable fleet savings in a number of ways.First, for example, preferred power-sharing configurations may minimize,reduce, or advantageously apportion fleet degradation, which maysignificantly impact generating capacity and efficiency over futureoperating periods. Second, an adviser function may be configured usingthe described components so to optimize or, at least, enhancemaintenance intervals by which degradation losses, both recoverable andnon-recoverable, are mitigated. Monitoring and predicting the rate ofdegradation and scheduling/conducting maintenance procedureseffectively, such as compressor washes or filter cleanings, will ensurethat the gas turbine operates most efficiently.

Turning now to FIG. 28, another related aspect of the present inventionis discussed, which describes the more specific example of controllingthe operation of multiple gas turbine engines operating as a powerblock. The gas turbine engines, as will be appreciated, may be locatedat a particular power plant or across several remote power plants. Asalready discussed, controlling a block of gas turbines so to optimize orenhance power sharing is a challenge. Current control systems do noteffectively synchronize across a block of multiple engines and, instead,substantially engage each of the engines individually based uponunsophisticated apportioning of the output level for which the powerblock is collectively responsible. As will be appreciated, this oftenleads to imbalances and inefficient rates of degradation. Accordingly,there is a need for more optimal control strategies and, in particular,a system controller that provides for efficient power sharing strategiesacross multiple gas turbines that promote a more cost-effective loss ordegradation rate when the units are collectively considered as a powerblock. For example, if a gas turbine block has several engines havingthe same ratings, the present invention may make recommendations basedon the engines current degradation state as to which of units shouldoperate at higher output levels and which should operate at reducedlevels. The present invention may accomplish this in accordance withaspects already discussed herein, particularly those discussed relativeto FIGS. 24 through 27. As one of ordinary skill in the art willappreciate, the advantages of such functionality include: increased lifeand performance of the gas turbines; improved life prediction, which mayenable more competitive and/or risk sharing service agreements; greateroperational flexibility for the power block as a whole; and robustmulti-objective optimization that efficiently takes into accountoperational trade-offs, which may relate, for example, to hot gas pathuseful part-life expenditures, current degradation levels, and rates ofdegradation, and present power generating performance, such as demand,efficiency, fuel consumption, etc.

One way in which this may be accomplished is pursuant to a system 900,which will now be described with respect to FIG. 28. As indicated, aplurality of gas turbines 901 may be operated as part of a power blockor “block 902”. As discussed as part of the systems above, operatingparameters 903 for each of the assets 901 may be gathered andelectronically communicated to a block controller 904. According to apreferred embodiment, the operating parameters may include a rotorspeed, compressor surge margin, and a blade lip clearance. As will beappreciated, the compressor surge margin may be calculated relative tomeasured rotor speed, and the blade tip clearance may be measuredpursuant to any conventional method, including, for example, microwavesensors. As a further input, the block controller may receive records905 from a database component, such as any of those already discussed,which may record current and past operating parameter measurements,including rotor speed, surge margin, blade tip clearance, controlsettings, ambient conditions data, etc., so to adaptively correlatedprocess inputs and outputs.

According to preferred embodiments, the block controller 904 may beconfigured to operate as a model-free adaptive controller. Themodel-free adaptive controller may include a neural network based setupthat has inputs (for example, via the records 905) from each of the gasturbines corresponding to demand, heat rate, etc. As will beappreciated, model-free adaptive control is a particularly effectivecontrol method for unknown discrete-time nonlinear systems withtime-varying parameters and time-varying structures. The design andanalysis of model-free adaptive control places an emphasis on processinputs and outputs so to “learn” predictive correlations or algorithmsthat explain the relationships therebetween. Correlations betweenmeasured inputs and outputs of the system being controlled. Functioningin this manner, the block controller 904 may derive control commands orrecommendations, and these may be communicated as an output 906 to amaster control system 907 for implementation. According to a preferredembodiment, the output 906 from the block controller 904 includes apreferred or optimized power sharing command or recommendation.According to other embodiments, the output 906 may include commands orrecommendations related to modulated coolant flow for hot gas pathcomponents of the gas turbines 901 and/or modulated IGV settings for thecompressor units of the gas turbines 901.

The master control system 907 may be communicatively linked to the gasturbines 901 of the power block 902 so to implement control solutionsgiven the output 906. As illustrated, the master control system 907 mayalso communicate such information to the block controller 904. Thuslyconfigured, the control system of FIG. 28 may operate to control theseveral gas turbines of the power block 902 so to generate a combinedload or output level—such as, for example, a contract output level asmight be determined by a dispatch bid process, for which the gasturbines collectively are responsible—in an enhanced or optimized manneraccording to a defined cost function. This control solution may includerecommending a percentage of the combined output level that each of thegas turbines should contribute. In addition, the master control system907 may include a physics based model for controlling the gas turbinespursuant to the optimized operating mode, as discussed previously.

According to an exemplary embodiment, for example, clearance and surgemargin data may be tracked for each of the gas turbines. If clearance orsurge margin data for any of the gas turbines is determined to be abovea predefined threshold, that particular turbine may be operated at areduced load. If operating that gas turbine at a reduced level is notpossible, other recommendations may be made such as modulating IGVsettings or coolant flow to hot gas path components. On the other hand,if one of the gas turbines is selected to operate at a reduced level,the optimized generating configuration may include recommending that oneor more of the other gas turbines operate at a higher/peak load so tomake up for any deficit. The method may select the higher/peak loadturbines based upon surge margin and clearance data, with the desiredeffect of balancing current degradation levels and rate of degradationamong the gas turbines of the power block so to collectively extendoperating life, while maintaining higher a higher block output level andefficiency. As mentioned, because performance degradation rates anduseful part--life expenditures may accrual nonlinearly as well as bedependent upon parameters that are variable across geographicallydispersed units, savings may be achieved by using the block levelperspective described herein to apportion load in a way that optimizes acost result for the block. Power generation thus may be apportioned soto optimize costs across the block 902 by taking into account real timedata (particularly, surge margin and clearance data) that has beendetermined to be highly dispositive and efficient at evaluatingperformance degradation levels, rates of degradation, remainingpart-life, and true performance capacity for the gas turbines of theblock.

Referring now to FIG. 29, another exemplary embodiment of the presentinvention includes systems and methods that provide for more efficientand/or optimized shutdown of combined cycle power plants. As will beappreciated, during shutdown of a combined cycle plant, a controllertypically reduces fuel flow to the gas turbine gradually so to reducerotor speed toward a minimum speed. This minimum speed may be referredto as the “turning gear speed” because it represents the speed at whichthe rotor is engaged by a turning gear and thereby rotated so as toprevent thermal bowing of the rotor during the shutdown period.Depending upon the nature of the gas turbine engine, the fuel flow maybe stopped at about twenty percent or so of typical full speed, with theturning gear engaged at about one percent of full speed. Reducing theflow of fuel in this gradual manner, however, does not provide a directrelationship with the reduction of the rotor speed. Rather, large andunyielding variations in the speed of the rotor over the shutdown periodis typical. The variations in rotor speed may then cause significantdifferences in the fuel to air ratio, which is due to the fact that airintake is a function of the rotor speed, while fuel flow is not. Suchvariations then may lead to significant and abrupt variations in firingtemperatures, transient temperature gradients, emissions, coolant flow,as well as others. The variations in shutdown behavior may have animpact on turbine clearances and, hence, overall turbine performance andcomponent lifetime.

There is, therefore, a desire for a combined cycle shutdown controllerthat improves plant shutdown by rectifying one or more of these issues.Preferably, such a controller would control the rate of deceleration ofthe turbine rotor and related components over time so as to minimizeuneven shutdown variations and, thereby, minimize the negative impact tothe engine systems and components. According to certain embodiments, amore effective controller functions so to optimize rotor stresses andthe slew rate of rotor speed and torque. The shutdown controller alsomay correct variability in subsystems such that, for example, coolantflow and wheelspace temperature remain at preferred levels. According topreferred embodiments, the present method may control the rate of thedeceleration of the rotor and related components over time so as tominimize shutdown variations in a way that reduces costs, plant losses,and other negative effects. Pursuant to the systems and methods alreadydescribed, the control methodology may function so that factorsimpacting shutdown costs are optimized according to operator-definedcriteria or cost functions. One way in which this may be accomplished ispursuant to a process 920, which will now be described with respect toFIG. 29. As will be apparent to one of ordinary skill in the art,aspects of the process 920 draw upon subject matter already discussedherein—particularly with reference to the discussion related to FIGS. 3and 4—which, for the sake of brevity, will be summarized, but notentirely repeated.

According to one embodiment, the shutdown procedures and/or the combinedcycle shutdown controller of the present invention is configured as aconventional loop-shaping controller. The controller of the presentinvention may include aspects of model-free adaptive control as well asmodel-based control, as delineated in the appended claims. The combinedcycle shutdown controller may include target shutdown time controller,and an actual shutdown time controller, and may control most if not allaspects of the plant shutdown. The controller may receive inputs such asexhaust spread, wheel-space temperature, clearance, surge margin, steamand gas turbine rotor stresses, gas turbine rotor rate of deceleration,demand, fuel flow, current power production, grid frequency, secondaryfiring, drum levels, and so on. Based on these inputs, the shutdowncontroller may compute a time range for shutdown (e.g., rate ofshutdown), slew rate of rotor deceleration, corrected coolant flow, andcorrected inlet guide vane profile, and/or a generator reverse torquedesired during shutdown, as described in more detail below. According tocertain embodiments, each of these outputs may be used to offsetpotentially harmful shutdown variations detected by one of the powerplant sensors. The combined cycle shutdown controller may provide atrajectory of RPM/slew rate versus time profile, and rate ofdeceleration versus current power production profile more suitable forshutdown operations, and both may take into account combined cyclesystems, such as the HRSG, steam turbines, boilers, and the like. Theshutdown controller may control the components described herein untilturning gear speed is achieved, thus providing for more optimal steamturbine and HRSG operability conditions, while also lowering componentstresses.

FIG. 29 is a flow chart depicting an embodiment of a process 920suitable for shutting down a combined cycle power plant, such as thepower plant 12 described in relation to FIG. 3. The process 920 may beimplemented as computer code executable by the combined cycle shutdowncontroller, and may be initiated after receiving (step 921) a shutdowncommand. The shutdown command may be received, for example, based on amaintenance event, a fuel change event, and so on. The process 920 maythen retrieve (step 922) a current state of plant components, which maybe sensed, gathered, stored, and retrieved per any of the sensors,systems, and/or methods already described herein. The current state ofplant components, for example, may include turbine rotor speed,temperature of components, exhaust temperature, pressures, flow rates,clearances (i.e., distances between rotating and stationary components),vibration measurements, and the like. The state of the plant mayadditionally include current power production, and costing data such as,for example, cost of not producing power, cost of power at market rates,green credits (e.g., emission credits), and the like.

At a next step, costing or loss data may be retrieved (step 923), forexample, by querying a variety of systems, including accounting systems,futures trading systems, energy market systems, or a combinationthereof. Historical data may additionally be retrieved (step 924). Thehistorical data may include log data for performance of systems,maintenance data, fleet-wide historical data (e.g., logs from othercomponents in plants disposed in various geographic localities),inspection reports, and/or historical cost data.

The process may then derive algorithms regarding plant shutdowndegradation or losses (step 925) related to shutdown operation. Suchderivations may be determined using several input types, including, forexample, historical operating data related to gas turbine systems, steamturbine systems, HRSG units, as well as for any other subcomponents asmay be present. According to certain embodiments, a variety of models oralgorithms may be developed by which combined cycle shutdown losses arederived. As discussed more fully in the discussion related to FIG. 4,such algorithms may function to provide a summation of power plantshutdown losses based on values for selected operating parameters orperformance indicators, such as temperatures, pressures, flow rates,clearances, stresses, vibration, shutdown time, and the like. As will beappreciated, consistent with the other embodiments described herein,alternative, proposed or competing shutdown modes for the combined cyclepower plant may be simulated in a combined cycle power plant model. Thatis, a combined cycle power plant model may be developed, tuned, andmaintained, and then used to simulate alternative or competing shutdownoperating modes so to derive predicted values for certain predefinedperformance indicators. The predicted values for the performanceparameters then may be used to calculate shutdown costs pursuant to thederived loss algorithms.

For example, algorithms may be developed that correlate shutdown lossesand a predicted thermal stresses profile, which may be determined fromthe predicted values for certain performance parameters given theoperating parameters related to one of the competing shutdown operatingmodes. According to certain embodiments, such losses may reflect anoverall economic consequence of the competing shutdown operating mode,and, for example, may take into account degradation to hot gas pathcomponents and/or a percentage of useful part-life expended given theshutdown mode, as well as any resulting performance degradation to theplant, and may be calculated from initiation of shutdown until anachieved time of shutdown, which, for example, may be when the turninggear speed is achieved. Similarly, loss algorithms may be developed soto determine losses related to: compressor and turbine mechanicalstresses; clearances between stationary and rotating parts; shutdownemissions; shutdown fuel consumption; steam turbine rotor/stator thermalstresses; boiler drum pressure gradients; etc.

The process 920 may then derive (step 926) an enhanced or optimizedshutdown operating mode, which may include a RPM/slew rate versus timeprofile, and/or a rate of deceleration versus current power productionprofile that is particularly well-suited for the shutdown of thecombined cycle power plant. For example, the optimized shutdownoperating mode may be determined as the one that best accommodates andtakes into account the operation of the steam turbine, HRSG unit, theboiler, and/or other components of the combined cycle plant. Accordingto one embodiment, the controller take in the aforementioned inputs andderive therefrom expected conditions at various RPM/slew time parametersso to derive a RPM/slew curve plotted along an time axis that minimizesstresses and/or optimizes shutdown costs. Likewise, rate of decelerationversus current power production profiles may include a fuel flow thatmore desirably (as compared to other proposed shutdown modes) improvescurrent power production based on deceleration of the shaft. Accordingto other embodiments, cost functions may be defined by which other morepreferable or optimized shutdown operating modes are derived andselected. As will be appreciated, scenarios may be derived that, forexample, minimizes stresses and/or losses for the gas turbine, minimizesstresses and/or losses for the steam turbine, minimizes stresses and/orlosses for the HRSG, or a combination thereof. Depending on how the costfunction is defined, further optimized shutdown operating modes may bedetermined based on criteria, such as, costs for power production duringthe shutdown period, plant emissions, fuel consumption, and/orcombinations thereof without limitation.

The combined cycle shutdown controller may further include a controlsystem for shutting down the power plant according to the optimizedshutdown mode. According to a preferred embodiment, this control systemmay include a physics-based modeler or a model based controller thatthen derives a control solution given the optimized shutdown mode. Themodel based controller may derive control inputs and settings forcontrolling actuators and control devices so that the combined cyclepower plant is operated during the shutdown period in accordance withthe preferred or optimized shutdown operating mode. For example, theshutdown controller may actuate fuel valves to conform to a desired fuelflow rate while also controlling inlet guide vanes of the gas turbineexhaust to control exhaust flow into the HRSG, while additionallycontrolling steam valves of the steam turbine to control steam turbineshutdown. By combining control of a variety of components approximatelysimultaneously with each other, the shutdown for the plant may beimproved and may conform with desired scenarios.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

We claim:
 1. A computer-implemented control method for optimizing a turndown operation for a power plant having a plurality of generating units for a selected operating period, wherein the plurality of generating units each comprises either an on-condition or an off-condition during the selected operating period, the method including a controller having a processor that performs the steps of: defining competing operating modes, wherein the competing operating modes comprise different possible combinations regarding which of the plurality of generating units comprise the on-condition and which comprise the off-condition during the selected operating period; defining multiple cases for each of the competing operating modes, wherein the multiple cases include varying a value of an operating parameter over a range; receiving performance objectives that include a cost function for evaluating the turndown operation during the selected operating period; receiving an ambient conditions forecast for the selected operating period; for each of the multiple cases of the competing operating modes, simulating the turndown operation of the power plant for the selected operating period with a power plant model given the value of the operating parameter and the ambient conditions forecast; evaluating a simulation result from each of the simulations pursuant to the cost function so to select therefrom a preferred case from the multiple cases for each of the competing operating modes; and controlling the power plant pursuant to the preferred case.
 2. The computer implemented control method of claim 1, wherein the plurality of the generating units comprises a plurality of gas turbines; wherein step of defining the competing operating modes includes: permutating the plurality of gas turbines so to configure an on/off permutation matrix in which permutations describe each unique combination regarding which of the plurality of gas turbines comprise the on-condition and which comprise the off-condition during the selected operating period; wherein each of the permutations of the permutation matrix is defined as one of the competing operating modes for the selected operating period; and wherein the step of controlling the power plant pursuant to the preferred case comprises controlling the plurality of gas turbines in accordance with the on-condition and the off-condition defined for each of the plurality of gas turbines within the on/off permutation matrix of the competing operating mode that results in the preferred case.
 3. The computer-implemented control method according to claim 2, wherein the step of defining multiple cases for each of the competing operating modes includes varying a value for a first operating parameter over a first range and a value for a second operating parameter over a second range.
 4. The computer-implemented control method according to claim 3, wherein the step of simulating with the power plant model each of the multiple cases of the competing operating modes includes generating proposed parameter sets for each particular multiple case of the multiple cases; and wherein, for each particular multiple case of the multiple cases, the proposed parameter set includes: the value within the first range for the first operating parameter and the value within the second range for the second operating parameter for the particular multiple case; the on-condition and the off-condition for the plurality of gas turbines for the competing operating mode to which the particular multiple case corresponds; and data regarding the ambient conditions forecast for the selected operating period.
 5. The computer-implemented control method according to claim 4, wherein the step of simulating with the power plant model the multiple cases includes performing a simulation run with the power plant model for each of the proposed parameter sets, the simulation run configured to simulate turndown operation during the selected operating period according to input data defined by the proposed parameter sets; wherein the performance objectives further comprise operability constraints; and wherein the step of evaluating the simulation result from each of the simulation runs comprises determining which, if any, of the simulation results violate any of the operability constraints.
 6. The computer-implemented control method according to claim 3, comprising the step of subdividing the selected operating period into regularly repeating intervals; wherein the step of receiving the ambient conditions forecast comprises receiving an ambient conditions forecast for each of the intervals; and wherein the step of permutating the plurality of gas turbines comprises permutating the plurality of gas turbines for each of the intervals so to configure the permutation matrix for each interval, wherein the permutation matrix for each interval is configure such that, for an entirety of any of the intervals, each of the plurality of gas turbines comprises just one of the on-condition and the off-condition to the exclusion of the other.
 7. The computer-implemented control method according to claim 6, wherein the step of defining competing operating modes includes defining as one of the competing operating modes each of the permutations for each of the permutation matrices for each of the intervals.
 8. The computer-implemented control method according to claim 7, wherein the step of evaluating the simulation result from each of the simulations comprises selecting a preferred case from the multiple cases for each of the competing operating modes for each of the intervals.
 9. The computer-implemented control method according to claim 8, wherein the step of simulating with the power plant model each of the multiple cases of the competing operating modes includes generating proposed parameter sets for each particular multiple case of the multiple cases, wherein, for each particular multiple case, the proposed parameter set includes: the value within the first range for the first operating parameter and the value within the second range for the second operating parameter for the particular multiple case; the on-condition and the off-condition for the plurality of gas turbines for the competing operating mode to which the particular multiple case corresponds; and data regarding the ambient conditions forecast for the interval to which the particular multiple case corresponds.
 10. The computer-implemented control method according to claim 9, wherein the step of simulating with the power plant model each of the multiple cases includes performing a simulation run with the power plant model for each of the proposed parameter sets, the simulation run configured to simulate turndown operation during the selected operating period according to input data defined by the proposed parameter sets; and wherein the performance objectives further comprise operability constraints; and wherein the step of evaluating the simulation results from the simulation runs comprises determining which, if any, of the simulation results violate any of the operability constraints and disqualifying for consideration as one of the preferred cases any of the multiple cases that produced the simulation results that violated the operability constraints.
 11. The computer-implemented control method according to claim 9, wherein the on/off permutation matrix comprises all of the unique combinations regarding which of the plurality of gas turbines comprise the on-condition and which comprise the off-condition during one of the intervals of the selected operating period, wherein the on-condition comprises an indication of an operating condition for a particular one of the plurality of gas turbines during one of the intervals, and the off-condition comprises a shutdown condition for a particular one of the plurality of gas turbines during one of the intervals.
 12. The computer-implemented control method, according to claim 9, further comprising the steps of tuning the power plant model using the processor of the controller before performing the simulation runs, wherein the tuning includes: defining a first operating period that is previous to the selected operating period; defining a plurality of the operating parameters; defining a performance indicator, wherein the performance indicator comprises a criteria of performance regarding the operation of the power plant over a defined operating period, and wherein the performance indicator is defined so to, at least in part, depend upon a selected operating parameter chosen from the plurality of operating parameters; sensing measured values for the plurality of the operating parameters during the first operating period; from the measured values, calculating a measured value for the performance indicator; with the power plant model, simulating the operation of the power plant over the first operating period using input data, wherein the input data for the simulation comprises a subset of the measured values for the plurality of operating parameters and wherein, as output data, the simulation is configured to predict a simulated value for the selected operating parameter; with the simulated value for the selected operating parameter, calculating a predicted value for the performance indicator; comparing the measured value against the predicted value of the performance indicator so to determine a differential therebetween; and using the differential to tune the power plant model.
 13. The computer-implemented control method according to claim 12, wherein the power plant model comprises a plurality of logic statements in which performance multipliers correlate process inputs to process outputs from the operation of the power plant; and wherein the step of using the differential to tune the power plant model comprises an iterative process of making an adjustment to one or more of the performance multipliers within the power plant model and then recalculating the predicted value for the performance indicator so to determine an affect the adjustment to the one or more performance multipliers on the calculation of the differential until the predicted value for performance indicator substantially equals the measured value for the performance indicator.
 14. The computer-implemented control method according to claim 9, wherein the first operating parameter comprises an inlet guide vane setting, and the second operating parameter comprises a turbine exhaust temperature.
 15. The computer-implemented control method according to claim 14, wherein the cost function comprises a total fuel consumption by the plurality of gas turbines, and the step of determining the preferred case for the competing operating modes comprises determining which of the simulation results minimizes the total fuel consumption.
 16. The computer-implemented control method according to claim 14, wherein the cost function comprises a generating output level for the plurality of gas turbines, and the step of determining the preferred case for the competing operating modes comprises determining which of the simulation results minimizes the generating output level during the interval.
 17. The computer-implemented control method according to claim 14, wherein the performance objectives comprise operability constraints; and wherein the step of evaluating each of the simulation results of the simulation runs includes determining whether any of the simulation runs violate any of the operability constraints so to disqualifying any such simulation run from consideration as the optimized simulation run.
 18. The computer-implemented control method according to claim 17, wherein the operability constraints comprise at least one of: a combustion boundary; maintenance of a vacuum seal on a condenser of the power plant; and a minimum steam temperature in a defined portion of a steam turbine.
 19. The computer-implemented control method according to claim 2, wherein the cost function comprises at least one of a total fuel consumption and a generating output level for the plurality of gas turbines.
 20. The computer-implemented control method according to claim 19, further comprising the step of using the processor of the controller to electronically communicate an output reporting the preferred case for each of the competing operating modes, wherein the output includes at least one of the total fuel consumption and the generating output level for the plurality of gas turbines for each of the preferred cases. 